fix: revert E2E AEAD wrapping (broke multi-client voice); add Android CAMERA

Voice regression: EncryptingTransport encrypts media with the pairwise
client↔relay session key, but the relay forwards bytes without re-encrypting
per recipient. Sender's key_A ≠ recipient's key_B → recipient cannot decrypt
→ silent audio between mac and android. Drop the wrapper; restore plaintext-
over-QUIC-TLS to the relay. Proper E2E needs MLS group keys or relay hop-by-
hop re-encryption (future PRD).

Android camera: add CAMERA manifest permission + runtime request via
MainActivity. NOTE: still not sufficient — Tauri/Wry's WebChromeClient does
not grant getUserMedia, so video on Android needs a Tauri plugin override
or native Camera2 path. Documented in MainActivity.kt.

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

desktop/src-tauri/gen/android/app/src/main/AndroidManifest.xml

@@ -3,7 +3,9 @@
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
+    <uses-permission android:name="android.permission.CAMERA" />
     <uses-feature android:name="android.hardware.microphone" android:required="true" />
+    <uses-feature android:name="android.hardware.camera" android:required="false" />
 
     <!-- AndroidTV support -->
     <uses-feature android:name="android.software.leanback" android:required="false" />