feat(audio): Android on-device system playback capture

Enable audio-reactive lighting on the Android-TV build. A push-based
AndroidAudioEngine captures system playback audio via AudioPlaybackCapture
(API 29+), reusing the existing MediaProjection token, and feeds PCM into
the unchanged AudioAnalyzer pipeline. No new Python deps; no Chaquopy/pip
changes (numpy already bundled).

- Python: android_audio_engine.py — module-level queue + configure/
  push_samples/shutdown mirroring mediaprojection_engine; AndroidAudioEngine
  (priority 100) registered behind a guarded import. push_samples copies and
  defensively trims/clamps each block so the analyzer can't crash on
  variable-length or non-frame-divisible PCM.
- Kotlin: AudioCapture.kt — AudioRecord + AudioPlaybackCaptureConfiguration,
  fixed chunk-size block framing, little-endian float32, mic fallback;
  reads back the actual negotiated channel/sample rate. PythonBridge gains
  configureAudio/pushAudio/shutdownAudio with a cached module handle.
- Wiring: CaptureService starts/stops AudioCapture in the MediaProjection
  path (gated on API>=29 + RECORD_AUDIO + live projection); MainActivity
  requests RECORD_AUDIO; manifest declares it. Degrades gracefully when
  denied; root path stays audio-less by design.
- Tests: 13 desktop-CI tests incl. an over-length/non-divisible regression
  guard that exercises the full read_chunk -> AudioAnalyzer.analyze path.

android/app/src/main/AndroidManifest.xml

@@ -39,6 +39,14 @@
     <!-- POST_NOTIFICATIONS for Android 13+ foreground service notification -->
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 
+    <!-- RECORD_AUDIO for on-device system-playback capture (AudioPlaybackCapture,
+         API 29+) feeding audio-reactive lighting. Runtime "dangerous" permission,
+         requested in MainActivity; capture degrades gracefully when denied.
+         Playback capture runs under the existing mediaProjection FGS type, so no
+         FOREGROUND_SERVICE_MICROPHONE / microphone FGS type is needed (that would
+         only be required if the mic-fallback path ran inside the service). -->
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+
     <!-- Autostart on boot — BootReceiver spawns CaptureService in root
          mode so capture resumes without the user touching the remote. -->
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />