feat: Android Oboe voice backend — WebRTC APM, VAD, HW/SW toggle, BBCode welcome, link trust, foreground task

Audio engine (Rust):
- Android Oboe: WebRTC APM (AEC/NS/AGC/HPF) + TEN/Silero ONNX VAD
- Hardware effects (JNI) with software fallback per-effect
- Render reference buffer for AEC between output/capture callbacks
- Voice activity gate: suppress transmission when speaker muted (all platforms)
- Audio focus (SDD-109) + Bluetooth SCO (SDD-110) via JNI
- ONNX Runtime 1.26 via ort 2.0.0-rc.12 (down from rc.10, ndarray 0.17)
- VAD worker channel capacity 8→32, initial seq u64::MAX (warm-up fix)
- TEN VAD default backend (was Silero)
- Platform→WebrtcApm resolution after hardware binding
- oboe-rs edisonjwa fork with get_raw_session_id()

Android Kotlin:
- AndroidAudioFocusController + AndroidBluetoothScoController
- AndroidAudioLifecycleController (route changes to Flutter)
- ProGuard rules for new controllers

Flutter UI:
- VoiceSettings: Android HW/SW toggle (Platform auto / WebRTC APM)
- VoiceStatusChip: mute warning border + Speaker muted label
- BBCode welcome message parser (BbCodeText, case-insensitive)
- Welcome message foldable (expanded by default)
- Link trust dialog (domain wildcards, SharedPreferences)
- HapticFeedback on voice sheet opener
- Server name in AppBar, version v0.1.0
- Default channel (id=1) visible, serverquery clients hidden
- flutter_foreground_task integration

Config:
- ort load-dynamic on all non-iOS (Android/Linux/Windows)
- ONNX Runtime AAR 1.26.0
- ndarray moved to common deps (was Apple-only)

.cargo/config.toml

@@ -3,20 +3,14 @@
 # Opus CMake build to succeed on CMake 4.x (which removed compatibility
 # with cmake_minimum_required < 3.5). audiopus_sys v0.2.2 bundles
 # Opus 1.3.1 whose CMakeLists.txt uses a very old minimum version.
-#
-# IPHONEOS_DEPLOYMENT_TARGET=13.0 is required for iOS builds because
-# ___chkstk_darwin (the stack-probe symbol emitted by clang for functions
-# with large stack frames) only exists in the iOS 13.0+ runtime.  The
-# pre-built libopus.a and any C code compiled by the cc crate reference
-# this symbol.  Without this env var, the cc crate compiles C code
-# targeting iOS 10.0 (the Rust default), producing object files that
-# reference ___chkstk_darwin but can't resolve it against the 10.0
-# runtime.  Setting IPHONEOS_DEPLOYMENT_TARGET=13.0 ensures the cc crate
-# and CMake both target iOS 13.0+, where ___chkstk_darwin exists.
-# (DEC-003: minimum deployment target iOS 13.0)
 [env]
 CMAKE_POLICY_VERSION_MINIMUM = "3.5"
-IPHONEOS_DEPLOYMENT_TARGET = "13.0"
+
+# iOS builds must set IPHONEOS_DEPLOYMENT_TARGET in the invoking script
+# or Xcode build phase. Do not set it globally here: native macOS cargo
+# checks also compile bundled C/C++ dependencies, and a global iOS
+# deployment target makes clang try to link iPhone objects against the
+# macOS SDK.
 
 # iOS target linker flags (DEC-003: minimum deployment target iOS 13.0).
 #