feat(android): on-device webcam capture via Camera2 (AndroidCameraEngine)

Add on-device webcam capture to the experimental Android-TV build. Desktop
captures webcams via OpenCV (no Chaquopy/Android wheel); this adds a push-based
AndroidCameraEngine that plugs into the same selection path desktop uses
(capture template engine_type="android_camera" + display_index, HAS_OWN_DISPLAYS).

A Kotlin CameraBridge (Camera2) enumerates cameras and opens them on demand —
only while a capture source is active, driven Python->Kotlin via a guarded jclass
singleton (BleBridge pattern) — converts each frame YUV_420_888->RGB, and pushes
RGB bytes into a module-level queue mirroring mediaprojection_engine.py. Cameras
surface as selectable displays like the desktop OpenCV engine; the data-driven
capture-template UI is unchanged. No new Python deps; no new Gradle deps
(Camera2 is in-platform).

Engine: ENGINE_PRIORITY=0 (never auto-selected over MediaProjection=100; explicit
engine_type only). Single-camera ownership is serialized with a lock + ref-count
(same-camera streams attach, different-camera refused, last release stops),
mirroring the desktop CameraEngine guard.

Permission: CAMERA requested at capture-start, gated on FEATURE_CAMERA_ANY so
camera-less TV boxes never prompt; graceful degradation when denied. The service
is promoted with the camera FGS type (+ FOREGROUND_SERVICE_CAMERA) only when
CAMERA is already granted, so backgrounded capture keeps working without risking
a failed startForeground on camera-less boxes (camera can't ride the
MediaProjection token the way audio playback capture does).

Reviewed via multi-agent adversarial pass (13 findings -> 4 fixed: device leak on
session-failure, multi-stream collision, camera FGS type, i18n key; 9 refuted).

Tests: 18 new desktop-CI tests (no device needed); full suite 1883 passed.
Verified: assembleDebug BUILD SUCCESSFUL, ruff clean.

Docs: ANDROID-REVIEW/android-webcam-capture-plan.md (design), updated
android-missing-functionality.md + README feature table + en/ru/zh locales.

android/app/src/main/AndroidManifest.xml

@@ -35,6 +35,13 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PROJECTION" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_SPECIAL_USE" />
+    <!-- FOREGROUND_SERVICE_CAMERA (API 34+): required to keep camera access while
+         the app is backgrounded during on-device webcam capture. The service is
+         promoted with the `camera` FGS type ONLY when CAMERA is already granted
+         (see CaptureService.onStartCommand) — unlike audio playback capture (which
+         rides the MediaProjection token under the mediaProjection type), the camera
+         has no such coupling and needs its own FGS type to survive backgrounding. -->
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_CAMERA" />
 
     <!-- POST_NOTIFICATIONS for Android 13+ foreground service notification -->
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
@@ -47,6 +54,17 @@
          only be required if the mic-fallback path ran inside the service). -->
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
 
+    <!-- CAMERA for on-device webcam capture (Camera2). Runtime "dangerous"
+         permission, requested in MainActivity gated on FEATURE_CAMERA_ANY so
+         camera-less TV boxes never see the prompt; capture degrades gracefully
+         when denied. The camera is opened ON DEMAND (only while a camera
+         capture source is active). To keep capturing after the app is
+         backgrounded, the service is promoted with the `camera` FGS type
+         (FOREGROUND_SERVICE_CAMERA above) — but only when CAMERA is already
+         granted, so a camera-less / not-yet-granted box never risks a failed
+         service start. -->
+    <uses-permission android:name="android.permission.CAMERA" />
+
     <!-- 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" />
@@ -71,6 +89,15 @@
         android:name="android.hardware.usb.host"
         android:required="false" />
 
+    <!-- Camera hardware — for on-device webcam capture. required=false so
+         camera-less TV boxes (the common case) still install; the camera
+         engine simply reports no displays on such devices. camera.any covers
+         built-in (front/back) and external/USB-UVC cameras the platform
+         routes through Camera2. -->
+    <uses-feature
+        android:name="android.hardware.camera.any"
+        android:required="false" />
+
     <application
         android:name=".LedGrabApp"
         android:allowBackup="false"
@@ -103,7 +130,7 @@
              PROPERTY_SPECIAL_USE_FGS_SUBTYPE rationale below. -->
         <service
             android:name=".CaptureService"
-            android:foregroundServiceType="mediaProjection|specialUse"
+            android:foregroundServiceType="mediaProjection|specialUse|camera"
             android:exported="false">
             <property
                 android:name="android.app.PROPERTY_SPECIAL_USE_FGS_SUBTYPE"