Add P2P module, TLS LAN server, boot receiver, and encoded frame callback

- P2P: NSD advertiser, LAN TLS signaling server (port 8765), WebRTC peer
  manager, remote signaling client, control/file channel handlers
- LAN auth-pair endpoint generates pairing code via OkHttp (with auto
  token refresh) for phone app auto-discovery login
- Shared self-signed certificate (lck_lan.p12) for secure LAN comms
- Service starts at app launch and on BOOT_COMPLETED via BootReceiver
- P2P session waits for auto-login before starting NSD/signaling
- Native encoder: encoded frame callback for H.264 passthrough to WebRTC
- WebRTC dependency switched to io.github.webrtc-sdk (Maven Central)

app/build.gradle.kts

@@ -154,6 +154,9 @@ dependencies {
     // Browser (Custom Tabs for OAuth flows)
     implementation(libs.androidx.browser)
 
+    // WebRTC (P2P communication with phone app)
+    implementation("io.github.webrtc-sdk:android:137.7151.05")
+
     // Test
     testImplementation(libs.junit)
     androidTestImplementation(libs.androidx.junit)