merge: reconcile master particle-wind work with origin/main redesign

Merged divergent branches (common ancestor a9d87b6). Took origin/main
as base (layer manager, recenter, quit button, GPX tracks, marine
conditions, dark theme, user position layer, active/past track layers)
and layered in particle wind simulation work:

- MapHandler: added setupWindLayer, updateWindLayer, updateWindGridLayer;
  kept their user-pos layer, follow/recenter state, active+past tracks
- WeatherRepository: kept their fetchCurrentConditions, added fetchWindGrid
- MainViewModel: kept their track/marine/summary changes, added windGrid
  StateFlow, loadWindGrid, buildGrid
- MainActivity: kept their full UI (layer picker, quit, recenter, fade
  animations), added particleWindView wiring, weatherLoaded guard,
  windArrow/windGrid observers
- activity_main.xml: took their LinearLayout redesign, added ParticleWindView
  overlay inside ConstraintLayout

https://claude.ai/code/session_01HXPjBsogsJVRwCiekDGkJX

1 files changed, 3 insertions, 0 deletions

diff --git a/android-app/app/src/main/AndroidManifest.xml b/android-app/app/src/main/AndroidManifest.xml
index e2e311d..2f23e87 100644
--- a/android-app/app/src/main/AndroidManifest.xml
+++ b/android-app/app/src/main/AndroidManifest.xml
@@ -8,6 +8,9 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_LOCATION" />
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
+    <!-- Documents/ write access — not needed on API 29+ (MediaStore handles it) -->
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
+        android:maxSdkVersion="28" />
 
     <application
         android:name=".NavApplication"