feat: add ocean layers — depth contours, seamarks toggle, FADs

- MapLayerManager: depth contour tiles (OpenSeaMap), seamarks made
  toggleable (was always visible), FAD pref; layer order is now
  satellite → charts → wind → depth → seamarks
- MapHandler: FAD GeoJSON layer (orange circles + zoom-10 labels),
  setupFadLayer / setFadLayerVisible / updateFadLayer helpers
- LayerPickerSheet: wire seamarks, depth, FAD switches; fix chip
  binding direction bug (DepthUnit.METERS side was swapped)
- layout_layer_picker_sheet: add OCEAN LAYERS section with three
  toggles (seamarks/nav aids, depth contours, FADs)
- MainActivity: call setupFadLayer on style load; wire all three
  ocean layer callbacks in buildLayerPickerSheet

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

1 files changed, 122 insertions, 0 deletions

diff --git a/android-app/app/src/main/res/layout/layout_layer_picker_sheet.xml b/android-app/app/src/main/res/layout/layout_layer_picker_sheet.xml
index 2e6f982..065b720 100644
--- a/android-app/app/src/main/res/layout/layout_layer_picker_sheet.xml
+++ b/android-app/app/src/main/res/layout/layout_layer_picker_sheet.xml
@@ -176,6 +176,128 @@
 
         </LinearLayout>
 
+        <!-- ── OCEAN LAYERS ───────────────────────────────────────── -->
+
+        <View
+            android:layout_width="match_parent"
+            android:layout_height="1dp"
+            android:layout_marginTop="8dp"
+            android:layout_marginBottom="16dp"
+            android:background="@color/md_theme_surfaceVariant" />
+
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginBottom="12dp"
+            android:text="OCEAN LAYERS"
+            android:textSize="11sp"
+            android:textAllCaps="true"
+            android:letterSpacing="0.12"
+            android:fontFamily="sans-serif-light"
+            android:textColor="@color/instrument_text_secondary" />
+
+        <!-- Seamarks / nav aids -->
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal"
+            android:gravity="center_vertical"
+            android:layout_marginBottom="12dp">
+
+            <LinearLayout
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:orientation="vertical">
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Seamarks / nav aids"
+                    android:textSize="15sp"
+                    android:textColor="@color/instrument_text_normal" />
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Buoys, lights, hazards (OpenSeaMap)"
+                    android:textSize="12sp"
+                    android:textColor="@color/instrument_text_secondary" />
+            </LinearLayout>
+
+            <com.google.android.material.switchmaterial.SwitchMaterial
+                android:id="@+id/switch_seamarks"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content" />
+
+        </LinearLayout>
+
+        <!-- Depth contours -->
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal"
+            android:gravity="center_vertical"
+            android:layout_marginBottom="12dp">
+
+            <LinearLayout
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:orientation="vertical">
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Depth contours"
+                    android:textSize="15sp"
+                    android:textColor="@color/instrument_text_normal" />
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Soundings &amp; contour lines (OpenSeaMap)"
+                    android:textSize="12sp"
+                    android:textColor="@color/instrument_text_secondary" />
+            </LinearLayout>
+
+            <com.google.android.material.switchmaterial.SwitchMaterial
+                android:id="@+id/switch_depth"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content" />
+
+        </LinearLayout>
+
+        <!-- FADs -->
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal"
+            android:gravity="center_vertical"
+            android:layout_marginBottom="8dp">
+
+            <LinearLayout
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:orientation="vertical">
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="FADs"
+                    android:textSize="15sp"
+                    android:textColor="@color/instrument_text_normal" />
+                <TextView
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Fish aggregating devices (Hawaii DLNR)"
+                    android:textSize="12sp"
+                    android:textColor="@color/instrument_text_secondary" />
+            </LinearLayout>
+
+            <com.google.android.material.switchmaterial.SwitchMaterial
+                android:id="@+id/switch_fads"
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content" />
+
+        </LinearLayout>
+
         <!-- ── UNITS ───────────────────────────────────────────────── -->
 
         <View