feat: foreground service, dB gain sliders, speaker routing, live network stats

- Wire CallService foreground service for background calls (microphone type)
- Add Voice Volume + Mic Gain sliders (-20 to +20 dB) applied in Kotlin
- Connect AudioRouteManager for real speaker toggle via AudioManager
- Feed quinn QUIC RTT into PathMonitor, display Loss/RTT/Jitter from live data
- Nuclear teardown between calls — recreate engine + audio pipeline each call
- Fix re-entrant teardown loop from CallService notification callback
- Park audio threads as daemons to avoid libcrypto TLS destructor crash on exit
- Remove duplicate wakelocks from Activity (service owns them now)
- Strip AEC + denoise from capture path, keep AGC only (incremental approach)
- Fix .so copy target: libwzp_android.so not libwzp.so

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/wzp/engine/CallStats.kt

@@ -31,7 +31,7 @@ data class CallStats(
     /** Frames recovered by FEC. */
     val fecRecovered: Long = 0,
     /** Current mic audio level (RMS, 0-32767). */
-    val audioLevel: Int = 0
+    val audioLevel: Int = 0,
 ) {
     /** Human-readable quality label. */
     val qualityLabel: String