feat: add wind/current map overlay and weather forecast on startup

Implements the wind/current map overlay and 7-day weather forecast
display that loads on application launch:

Data layer:
- Open-Meteo API (free, no key): WeatherApiService + MarineApiService
- Moshi-annotated response models (WeatherResponse, MarineResponse)
- WeatherRepository: parallel async fetch, Result<T> error propagation
- Domain models: WindArrow (with beaufortScale/isCalm) + ForecastItem
  (with weatherDescription/isRainy via WMO weather codes)

Presentation layer:
- MainViewModel: StateFlow<UiState> (Loading/Success/Error),
  windArrow and forecast streams
- MainActivity: runtime location permission, FusedLocationProvider
  GPS fetch on startup, falls back to SF Bay default
- MapFragment: MapLibre GL map with wind-arrow SymbolLayer;
  icon rotated by wind direction, size scaled by speed in knots
- ForecastFragment + ForecastAdapter: RecyclerView ListAdapter
  showing 7-day hourly forecast (time, description, wind, temp, precip)

Resources:
- ic_wind_arrow.xml vector drawable (north-pointing, rotated by MapLibre)
- BottomNavigationView: Map / Forecast tabs
- ViewBinding enabled throughout

Tests (TDD — written before implementation):
- WindArrowTest: calm detection, direction normalisation, Beaufort scale
- ForecastItemTest: weatherDescription, isRainy for WMO codes
- WeatherApiServiceTest: MockWebServer request params + response parsing
- WeatherRepositoryTest: MockK service mocks, data mapping, error paths
- MainViewModelTest: Turbine StateFlow assertions for all state transitions

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

1 files changed, 22 insertions, 0 deletions

diff --git a/android-app/app/src/main/res/layout/activity_main.xml b/android-app/app/src/main/res/layout/activity_main.xml
new file mode 100644
index 0000000..757dbdb
--- /dev/null
+++ b/android-app/app/src/main/res/layout/activity_main.xml
@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout
+    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="match_parent">
+
+    <androidx.fragment.app.FragmentContainerView
+        android:id="@+id/fragment_container"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:layout_marginBottom="56dp" />
+
+    <com.google.android.material.bottomnavigation.BottomNavigationView
+        android:id="@+id/bottom_nav"
+        android:layout_width="match_parent"
+        android:layout_height="56dp"
+        android:layout_gravity="bottom"
+        android:background="?attr/colorSurface"
+        app:menu="@menu/bottom_nav_menu" />
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>