Android picture-in-picture, and fix three dead Android config files

Add PiP for native (ExoPlayer) video on Android. Video renders into a
SurfaceView behind the WebView, so PiP is driven by the Activity shrinking
into a floating window rather than the HTML5 PiP API (which WebKitGTK does
not implement, hence Android-only).

- PictureInPictureManager.kt: enter PiP with the video's aspect ratio
  (clamped to the 1:2.39-2.39:1 range Android accepts, outside which it
  throws), plus a play/pause RemoteAction. Hides the WebView while in PiP -
  it is opaque and sits above the surface, so it would otherwise occlude the
  video entirely - and re-fits the surface on exit.
- MainActivity.kt: onUserLeaveHint auto-PiP, onPictureInPictureModeChanged,
  and an AndroidPictureInPicture JS interface following the existing
  AndroidAudioFocus pattern.
- pictureInPicture.ts + VideoPlayer.svelte: PiP button, rendered only when
  the native bridge reports support.
- proguard: keep rules for @JavascriptInterface methods, which are only
  referenced from JS and would be stripped in minified release builds.

Casting needs no special handling: canEnterPip() checks natively that a
local video surface is attached and playing, which a remote session lacks.

While wiring the manifest, found that three tracked files under
src-tauri/android/ were never reaching any build. Gradle reads only
gen/android/app/src/main/, and sync-android-sources.sh did not copy them:

- src/main/AndroidManifest.xml was a partial <application> fragment written
  as if Tauri merged it. It does not - there is no manifest-merger hook
  here, so its hardwareAccelerated flag never reached an APK. Promoted to
  the complete authoritative manifest (folding in that flag) and synced.
- src/main/res/values/themes.xml (transparent status bar, fitsSystemWindows)
  was never copied; the sync only globbed mipmap-*. Now synced.
- build.gradle.kts was a leftover com.android.library module config with
  stale media3 1.5.1 deps. The live deps are in app/build.gradle.kts at
  1.5.0. Deleted.

Verified: merged manifest now carries hardwareAccelerated,
supportsPictureInPicture, resizeableActivity and the density configChange;
themes.xml compiles into merged resources; Kotlin builds warning-free;
svelte-check clean; 537 frontend tests pass.

Not verified: PiP behaviour on a device, and the release keep rules against
a minified build. assembleUniversalDebug cannot complete in this
environment - the Rust step wants a dev-server addr file that only exists
under `tauri android dev`.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src-tauri/android/src/main/AndroidManifest.xml

@@ -1,5 +1,67 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!--
+  Authoritative AndroidManifest for JellyTau.
+
+  NOTE: this is NOT a manifest-merger fragment. Gradle only ever reads
+  gen/android/app/src/main/AndroidManifest.xml, and `tauri android init`
+  regenerates that file from tauri.conf.json - dropping everything below.
+  scripts/sync-android-sources.sh copies this file over the generated one,
+  so this is the full manifest and the single source of truth.
+
+  (An earlier version of this file was a partial <application> fragment on the
+  assumption that Tauri merged it. It did not: the hardwareAccelerated flag it
+  declared never reached any built APK. It is folded in properly below.)
+-->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
-    <!-- Enable hardware acceleration for video playback performance -->
-    <application android:hardwareAccelerated="true" />
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.WAKE_LOCK" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+
+    <!-- AndroidTV support -->
+    <uses-feature android:name="android.software.leanback" android:required="false" />
+
+    <application
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:theme="@style/Theme.jellytau"
+        android:hardwareAccelerated="true"
+        android:usesCleartextTraffic="${usesCleartextTraffic}">
+        <activity
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|smallestScreenSize|screenLayout|uiMode|density"
+            android:launchMode="singleTask"
+            android:label="@string/main_activity_title"
+            android:name=".MainActivity"
+            android:exported="true"
+            android:supportsPictureInPicture="true"
+            android:resizeableActivity="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+                <!-- AndroidTV support -->
+                <category android:name="android.intent.category.LEANBACK_LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <provider
+          android:name="androidx.core.content.FileProvider"
+          android:authorities="${applicationId}.fileprovider"
+          android:exported="false"
+          android:grantUriPermissions="true">
+          <meta-data
+            android:name="android.support.FILE_PROVIDER_PATHS"
+            android:resource="@xml/file_paths" />
+        </provider>
+
+        <!-- Media playback service for lockscreen controls -->
+        <service
+            android:name="com.dtourolle.jellytau.player.JellyTauPlaybackService"
+            android:foregroundServiceType="mediaPlayback"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="androidx.media3.session.MediaSessionService" />
+            </intent-filter>
+        </service>
+    </application>
 </manifest>