feat(voice): unified mobile voice bar with gesture-isolated PTT row (#22)

* feat(voice): unified mobile voice bar with gesture-isolated PTT row

Replace separate VoiceStatusChip + VoicePttButton with a single
CompactVoiceBar widget that combines both into a two-row layout:

- Control row (tap): status text, mute, deafen, settings chevron
- PTT row (hold): full-width hold-to-talk, shown only in PTT mode

Gesture isolation prevents mis-touch between rows: the control row
uses tap-only InkWell/IconButton while the PTT row uses a raw
Listener for pointer-down/up events.

Key changes:
- Add CompactVoiceBar widget with state-colored container (normal,
  muted, talk-power-blocked)
- Remove mute/deafen IconButtons from AppBar headerActions
- Restructure voice details sheet into primary section + collapsible
  ExpansionTiles (audio processing, PTT capability, debug)
- Optimistic state updates for mute/deafen to eliminate tap delay
- Instant PTT visual feedback (no AnimatedContainer fade)
- Constant geometry across all states (no layout shift on toggle)

* fix(voice): preserve current PTT button format

* feat(voice): move mute/deafen controls into VoiceStatusChip

* fix(voice): ensure consistent chip height across mute states

Remove isSelected/selectedIcon from IconButtons inside VoiceStatusChip.
Material 3 toggle IconButtons (_SelectableIconButton) can vary in height
when the selected state changes due to tap target sizing. Use simple
conditional icons instead and set shrinkWrap tap target size with tight
constraints for stable 40x40 buttons regardless of state.

* fix(voice): remove leftover duplicate mute/deafen buttons in VoiceStatusChip

* fix(voice): replace unsafe stereo cast with bytemuck and localise talk-power tooltip

Replace the raw-pointer `&mut [(f32, f32)]` to `&mut [f32]` cast in
the oboe output callback with `bytemuck::cast_slice_mut`, eliminating
the unsafe block and relying on bytemuck compile-time NoUninit
verification instead.

Add voiceTalkPowerBlocked l10n key (en + zh) and replace the only
remaining hard-coded English tooltip in VoiceStatusChip with it.

apps/chanora_flutter/lib/l10n/app_en.arb

@@ -298,5 +298,6 @@
   "clientVolumeMuteAction": "Mute user",
   "clientVolumeUnmuteAction": "Unmute user",
   "clientVolumeResetAction": "Reset to default",
-  "permissionDenied": "Permission Denied"
+  "permissionDenied": "Permission Denied",
+  "voiceTalkPowerBlocked": "Insufficient talk power to speak in this channel"
 }

apps/chanora_flutter/lib/l10n/app_zh.arb

@@ -241,5 +241,6 @@
   "clientVolumeMuteAction": "静音该用户",
   "clientVolumeUnmuteAction": "取消静音",
   "clientVolumeResetAction": "恢复默认",
-  "permissionDenied": "权限被拒绝"
+  "permissionDenied": "权限被拒绝",
+  "voiceTalkPowerBlocked": "发言权限不足，无法在此频道发言"
 }

apps/chanora_flutter/lib/l10n/generated/app_localizations.dart

@@ -1246,6 +1246,12 @@ abstract class AppL10n {
   /// In en, this message translates to:
   /// **'Permission Denied'**
   String get permissionDenied;
+
+  /// No description provided for @voiceTalkPowerBlocked.
+  ///
+  /// In en, this message translates to:
+  /// **'Insufficient talk power to speak in this channel'**
+  String get voiceTalkPowerBlocked;
 }
 
 class _AppL10nDelegate extends LocalizationsDelegate<AppL10n> {

apps/chanora_flutter/lib/l10n/generated/app_localizations_en.dart

@@ -653,4 +653,8 @@ class AppL10nEn extends AppL10n {
 
   @override
   String get permissionDenied => 'Permission Denied';
+
+  @override
+  String get voiceTalkPowerBlocked =>
+      'Insufficient talk power to speak in this channel';
 }

apps/chanora_flutter/lib/l10n/generated/app_localizations_zh.dart

@@ -641,4 +641,7 @@ class AppL10nZh extends AppL10n {
 
   @override
   String get permissionDenied => '权限被拒绝';
+
+  @override
+  String get voiceTalkPowerBlocked => '发言权限不足，无法在此频道发言';
 }