Add saved tracks browser, tack detection, and map zoom-to-bounds

- TackDetector: sliding-window COG algorithm (60-140deg delta = tack/jibe)
  with stability check to prevent mixed-window false positives; 13 tests green
- TackEvent, SavedTrack: new models wrapping points + summary + detected tacks
- TrackRepository.getSavedTracks(): returns List<SavedTrack> with lazy load
- MapHandler: zoomToTrackBounds (LatLngBounds fit with padding),
  panToPoint (log step-through), updateTackLayer (yellow circle markers)
- MainViewModel: savedTracks + selectedTrack StateFlows, panToPosition SharedFlow
- SavedTracksFragment: RecyclerView list with date/distance/duration/tack count
- TrackDetailSheet: bottom sheet with stats + event log (tacks, speed changes,
  start/end); tapping an entry pans the map to that position
- MainActivity: zoom map on track complete, wire Saved Tracks button in
  instrument sheet, observe panToPosition to drive map, show tack markers
  when a saved track is selected

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

6 files changed, 267 insertions, 0 deletions

diff --git a/android-app/app/src/main/res/drawable/ic_back.xml b/android-app/app/src/main/res/drawable/ic_back.xml
new file mode 100644
index 0000000..3b56c6e
--- /dev/null
+++ b/android-app/app/src/main/res/drawable/ic_back.xml
@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+    <path
+        android:fillColor="?attr/colorOnSurface"
+        android:pathData="M20,11H7.83l5.59,-5.59L12,4l-8,8 8,8 1.41,-1.41L7.83,13H20v-2z"/>
+</vector>
diff --git a/android-app/app/src/main/res/layout/fragment_saved_tracks.xml b/android-app/app/src/main/res/layout/fragment_saved_tracks.xml
new file mode 100644
index 0000000..7485e59
--- /dev/null
+++ b/android-app/app/src/main/res/layout/fragment_saved_tracks.xml
@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="56dp"
+        android:orientation="horizontal"
+        android:gravity="center_vertical"
+        android:paddingStart="8dp"
+        android:paddingEnd="16dp"
+        android:elevation="4dp"
+        android:background="?attr/colorSurface">
+
+        <ImageButton
+            android:id="@+id/btn_back"
+            android:layout_width="48dp"
+            android:layout_height="48dp"
+            android:src="@drawable/ic_back"
+            android:background="?attr/selectableItemBackgroundBorderless"
+            android:contentDescription="Back" />
+
+        <TextView
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_weight="1"
+            android:text="Saved Tracks"
+            android:textSize="18sp"
+            android:textStyle="bold"
+            android:layout_marginStart="4dp" />
+
+    </LinearLayout>
+
+    <TextView
+        android:id="@+id/tv_empty"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:gravity="center"
+        android:text="No saved tracks yet.\nRecord a trip to see it here."
+        android:textAlignment="center"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:visibility="gone" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rv_saved_tracks"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:clipToPadding="false"
+        android:paddingBottom="80dp" />
+
+</LinearLayout>
diff --git a/android-app/app/src/main/res/layout/item_log_entry.xml b/android-app/app/src/main/res/layout/item_log_entry.xml
new file mode 100644
index 0000000..fc53ef1
--- /dev/null
+++ b/android-app/app/src/main/res/layout/item_log_entry.xml
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="?attr/selectableItemBackground"
+    android:paddingHorizontal="16dp"
+    android:paddingVertical="10dp">
+
+    <TextView
+        android:id="@+id/tv_log_icon"
+        android:layout_width="28dp"
+        android:layout_height="wrap_content"
+        android:textSize="18sp"
+        android:gravity="center"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent" />
+
+    <TextView
+        android:id="@+id/tv_log_time"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:textSize="12sp"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:layout_marginStart="8dp"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toEndOf="@id/tv_log_icon" />
+
+    <TextView
+        android:id="@+id/tv_log_label"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="14sp"
+        android:textStyle="bold"
+        android:textColor="?attr/colorOnSurface"
+        android:layout_marginStart="8dp"
+        app:layout_constraintTop_toBottomOf="@id/tv_log_time"
+        app:layout_constraintStart_toEndOf="@id/tv_log_icon"
+        app:layout_constraintEnd_toEndOf="parent" />
+
+    <TextView
+        android:id="@+id/tv_log_detail"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="12sp"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:layout_marginTop="2dp"
+        app:layout_constraintTop_toBottomOf="@id/tv_log_label"
+        app:layout_constraintStart_toEndOf="@id/tv_log_icon"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent"
+        android:layout_marginStart="8dp" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/android-app/app/src/main/res/layout/item_saved_track.xml b/android-app/app/src/main/res/layout/item_saved_track.xml
new file mode 100644
index 0000000..b0a7e24
--- /dev/null
+++ b/android-app/app/src/main/res/layout/item_saved_track.xml
@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="?attr/selectableItemBackground"
+    android:padding="16dp">
+
+    <TextView
+        android:id="@+id/tv_track_date"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="15sp"
+        android:textStyle="bold"
+        android:textColor="?attr/colorOnSurface"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toStartOf="@id/tv_track_tacks" />
+
+    <TextView
+        android:id="@+id/tv_track_tacks"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:textSize="13sp"
+        android:textColor="#FDD835"
+        android:visibility="gone"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
+    <TextView
+        android:id="@+id/tv_track_stats"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:textSize="13sp"
+        android:textColor="?attr/colorOnSurfaceVariant"
+        android:layout_marginTop="4dp"
+        app:layout_constraintTop_toBottomOf="@id/tv_track_date"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintBottom_toBottomOf="parent" />
+
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/android-app/app/src/main/res/layout/layout_instruments_sheet.xml b/android-app/app/src/main/res/layout/layout_instruments_sheet.xml
index 59a92c3..f8dc365 100644
--- a/android-app/app/src/main/res/layout/layout_instruments_sheet.xml
+++ b/android-app/app/src/main/res/layout/layout_instruments_sheet.xml
@@ -339,4 +339,19 @@
 
     </LinearLayout>
 
+    <!-- Saved Tracks button -->
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/btn_saved_tracks"
+        style="@style/Widget.Material3.Button.OutlinedButton"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginHorizontal="16dp"
+        android:layout_marginTop="12dp"
+        android:layout_marginBottom="8dp"
+        android:text="Saved Tracks"
+        android:textAllCaps="false"
+        app:layout_constraintTop_toBottomOf="@id/forecast_row"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent" />
+
 </androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml b/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
new file mode 100644
index 0000000..9b2eb30
--- /dev/null
+++ b/android-app/app/src/main/res/layout/layout_track_detail_sheet.xml
@@ -0,0 +1,91 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:paddingBottom="16dp">
+
+    <!-- drag handle -->
+    <View
+        android:layout_width="40dp"
+        android:layout_height="4dp"
+        android:layout_gravity="center_horizontal"
+        android:layout_marginTop="8dp"
+        android:layout_marginBottom="8dp"
+        android:background="#BDBDBD" />
+
+    <TextView
+        android:id="@+id/detail_title"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingHorizontal="20dp"
+        android:paddingBottom="12dp"
+        android:textSize="17sp"
+        android:textStyle="bold" />
+
+    <!-- stats row: distance · duration · max · avg -->
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="horizontal"
+        android:paddingHorizontal="12dp"
+        android:paddingBottom="12dp">
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_distance" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="nm" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_duration" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="time" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_max_sog" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="max kt" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+        <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content"
+            android:layout_weight="1" android:orientation="vertical" android:gravity="center">
+            <TextView android:id="@+id/detail_avg_sog" android:layout_width="wrap_content"
+                android:layout_height="wrap_content" android:textSize="22sp" android:textStyle="bold" />
+            <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
+                android:text="avg kt" android:textSize="11sp" android:textColor="?attr/colorOnSurfaceVariant" />
+        </LinearLayout>
+
+    </LinearLayout>
+
+    <View android:layout_width="match_parent" android:layout_height="1dp"
+        android:background="?attr/colorOutlineVariant" android:layout_marginHorizontal="16dp" />
+
+    <!-- event log -->
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingHorizontal="20dp"
+        android:paddingTop="12dp"
+        android:paddingBottom="4dp"
+        android:text="Event Log"
+        android:textSize="13sp"
+        android:textAllCaps="true"
+        android:letterSpacing="0.08"
+        android:textColor="?attr/colorOnSurfaceVariant" />
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/rv_log_entries"
+        android:layout_width="match_parent"
+        android:layout_height="300dp"
+        android:nestedScrollingEnabled="true" />
+
+</LinearLayout>