feat(voice): real-time mic input level metering at 30 Hz (#25)

* feat(voice): add real-time mic input level metering at 30 Hz

Expose input RMS from the audio engine through the bridge as a
dedicated Rust→Dart Stream<double>, replacing the binary on/off
indicator with a proportional dBFS level meter.

Rust side:
- chanora_audio: add set_input_dbfs/input_dbfs accessors to
  SharedAudioProcessingStats; restructure CaptureState::ingest()
  to compute dBFS from mono buffer before the PTT guard so the
  meter shows mic activity even when not transmitting.
- chanora_core: widen audio_stats() return to include f32 input
  level.
- chanora_bridge: add input_level: f32 to BridgeAudioStats and
  new input_level_stream(sink: StreamSink<f32>) that pushes at
  ~30 Hz via tokio interval task.
- Update frb_generated.rs serialization for the new field.

Flutter side:
- VoiceLevelMeter: accept optional double level (dBFS), map
  -60..0 dBFS to 0..1 fill fraction, animate with
  TweenAnimationBuilder for smooth transitions.
- voice_compact.dart: subscribe to inputLevelStream in the voice
  details sheet for 30 Hz meter updates, keeping 250 ms poll for
  TX/RX counters.
- voice_bar.dart: accept optional inputLevel from the stream.
- main.dart: subscribe to inputLevelStream, pass to VoiceBar.

* chore: sync Flutter build config and dependency updates

- Add Flutter migrator flags to gradle.properties (builtInKotlin, newDsl)
- Add FlutterGeneratedPluginSwiftPackage to iOS/macOS Xcode projects
- Update meta 1.17→1.18, test_api 0.7.10→0.7.11
- Rebuild chanora_bridge framework for macOS
- Update Podfile.lock for iOS and macOS

* fix(voice): correct meter animation, pre-gain dBFS, stream lifecycle, and protocol warnings

B1: Convert VoiceLevelMeter to StatefulWidget tracking previous fill
     as Tween begin so the meter animates smoothly instead of resetting
     to zero on every frame.

B2: Compute dBFS from pre-gain mono samples in CaptureState::ingest()
     so the level meter reflects raw mic input, matching mobile paths.

B4: End input_level_stream after 10 consecutive session errors instead
     of emitting -120 dBFS forever when the session is gone.

Also fixes all 13 clippy warnings in chanora_protocol: collapsed
nested if-let patterns, replaced .ok() + Some matching with Ok, used
? operator, and introduced EventChannels struct to reduce the four
helper functions below the 7-argument threshold.

* fix(voice): use MissedTickBehavior::Skip for level meter stream and align dBFS doc

Set MissedTickBehavior::Skip on the input_level_stream tokio interval
so slow audio_stats() calls skip missed ticks instead of bursting,
preventing CPU spikes on the UI meter thread.

Align VoiceLevelMeter class doc: the mapping floors at -60 dBFS
(via dbfsToFraction), not the full -120 range.

apps/chanora_flutter/lib/widgets/voice_bar.dart

@@ -33,6 +33,7 @@ class VoiceBar extends StatelessWidget {
     required this.onConfigure,
     required this.onPttHeldChanged,
     this.talkPowerBlocked = false,
+    this.inputLevel,
   });
 
   final bool inChannel;
@@ -53,6 +54,10 @@ class VoiceBar extends StatelessWidget {
   /// level meter. Pass `null` to render an idle meter.
   final rust.BridgeAudioStats? audioStats;
 
+  /// Real-time input level from the 30 Hz stream (dBFS).
+  /// When non-null, takes precedence over `audioStats.inputLevel`.
+  final double? inputLevel;
+
   /// PTT capability badge inputs — passed through to
   /// [`PttCapabilityBadge`].
   final String pttLevel;
@@ -196,7 +201,7 @@ class VoiceBar extends StatelessWidget {
                 ),
               const SizedBox(height: 6),
               // Row 4: level meter
-              VoiceLevelMeter(active: levelActive),
+              VoiceLevelMeter(active: levelActive, level: inputLevel ?? stats?.inputLevel),
               const SizedBox(height: 4),
               if (stats != null)
                 Text(

apps/chanora_flutter/lib/widgets/voice_compact.dart

@@ -7,7 +7,7 @@
 // release-tail are surfaced inline (radio buttons + slider) inside
 // the modal.
 
-import 'dart:async' show Timer, unawaited;
+import 'dart:async' show StreamSubscription, Timer, unawaited;
 import 'dart:io' show Platform;
 
 import 'package:flutter/foundation.dart' show kIsWeb;
@@ -455,6 +455,8 @@ class _VoiceSheetBodyState extends State<_VoiceSheetBody> {
   int _rateTickCount = 0;
 
   late final AudioProcessingConfigState _audioProcessing;
+  double? _streamLevel;
+  StreamSubscription<double>? _levelSub;
 
   @override
   void initState() {
@@ -463,8 +465,12 @@ class _VoiceSheetBodyState extends State<_VoiceSheetBody> {
       widget.initialAudioConfig,
     );
 
-    // Poll audio stats at 250 ms so TX/RX counters and the level meter
-    // update in real time while the sheet is open, independent of the parent.
+    _levelSub = rust.inputLevelStream().listen((level) {
+      if (mounted) setState(() => _streamLevel = level);
+    });
+
+    // Poll audio stats at 250 ms so TX/RX counters update in real time
+    // while the sheet is open.
     _statsTimer = Timer.periodic(const Duration(milliseconds: 250), (_) async {
       try {
         final s = await rust.audioStats();
@@ -472,7 +478,6 @@ class _VoiceSheetBodyState extends State<_VoiceSheetBody> {
         setState(() {
           _stats = s;
           _rateTickCount++;
-          // Compute rates every ~1 s (4 × 250 ms).
           if (_rateTickCount >= 4) {
             _txRate = s.framesSent - _prevSent;
             _rxRate = s.framesReceived - _prevReceived;
@@ -487,6 +492,7 @@ class _VoiceSheetBodyState extends State<_VoiceSheetBody> {
 
   @override
   void dispose() {
+    _levelSub?.cancel();
     _statsTimer?.cancel();
     super.dispose();
   }
@@ -625,7 +631,7 @@ class _VoiceSheetBodyState extends State<_VoiceSheetBody> {
             const SizedBox(height: 12),
 
             // 4) Level meter + live TX/RX stats.
-            VoiceLevelMeter(active: levelActive),
+            VoiceLevelMeter(active: levelActive, level: _streamLevel ?? stats?.inputLevel),
             const SizedBox(height: 6),
             _StatsRow(
               txRate: _txRate,

apps/chanora_flutter/lib/widgets/voice_level_meter.dart

@@ -1,28 +1,78 @@
+import 'dart:math' show max;
+
 import 'package:flutter/material.dart';
 
 /// Shared compact level meter used by voice surfaces.
-class VoiceLevelMeter extends StatelessWidget {
-  const VoiceLevelMeter({super.key, required this.active});
+///
+/// When [level] is null (no stats available yet), falls back to [active]
+/// for a binary indicator. When [level] is provided it is interpreted as
+/// dBFS and mapped to a 0–1 fill fraction via [dbfsToFraction] (floors
+/// at -60 dBFS).
+class VoiceLevelMeter extends StatefulWidget {
+  const VoiceLevelMeter({super.key, this.active = false, this.level});
 
+  /// Binary fallback when no dBFS value is available.
   final bool active;
 
+  /// Real input level in dBFS (-120 = silence, 0 = clipping).
+  /// Null means stats are not yet available; [active] is used instead.
+  final double? level;
+
+  /// Map dBFS [-60, 0] → [0.0, 1.0].
+  static double dbfsToFraction(double dbfs) {
+    const floor = -60.0;
+    if (dbfs <= floor) return 0.0;
+    if (dbfs >= 0.0) return 1.0;
+    return (dbfs - floor) / -floor;
+  }
+
+  @override
+  State<VoiceLevelMeter> createState() => _VoiceLevelMeterState();
+}
+
+class _VoiceLevelMeterState extends State<VoiceLevelMeter> {
+  double _previousFill = 0.0;
+
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
+    final double fill;
+    final Color color;
+    if (widget.level != null) {
+      fill = VoiceLevelMeter.dbfsToFraction(widget.level!);
+      color = fill > 0.0
+          ? theme.colorScheme.primary
+          : theme.colorScheme.outlineVariant;
+    } else {
+      fill = widget.active ? 0.75 : 0.05;
+      color = widget.active
+          ? theme.colorScheme.primary
+          : theme.colorScheme.outlineVariant;
+    }
+
+    final begin = _previousFill;
+    _previousFill = fill;
+
     return Container(
       height: 8,
       decoration: BoxDecoration(
         color: theme.colorScheme.surfaceContainerHighest,
         borderRadius: BorderRadius.circular(4),
       ),
-      child: FractionallySizedBox(
-        alignment: AlignmentDirectional.centerStart,
-        widthFactor: active ? 0.75 : 0.05,
+      child: TweenAnimationBuilder<double>(
+        tween: Tween<double>(begin: begin, end: fill),
+        duration: const Duration(milliseconds: 120),
+        curve: Curves.easeOut,
+        builder: (context, animatedFill, child) {
+          return FractionallySizedBox(
+            alignment: AlignmentDirectional.centerStart,
+            widthFactor: max(animatedFill, 0.02),
+            child: child,
+          );
+        },
         child: Container(
           decoration: BoxDecoration(
-            color: active
-                ? theme.colorScheme.primary
-                : theme.colorScheme.outlineVariant,
+            color: color,
             borderRadius: BorderRadius.circular(4),
           ),
         ),