feat: implement Phase 12 — voice message playback with ffplay

Add voice message playback infrastructure:
- AudioPlayer using ffplay subprocess with SIGSTOP/SIGCONT for pause/resume
- VoiceCache with LRU eviction (100 MB limit)
- TDLib integration: VoiceInfo, VoiceDownloadState, PlaybackState types
- download_voice_note() in TdClientTrait
- Keybindings: Space (play/pause), ←/→ (seek ±5s)
- Auto-stop playback on message navigation
- Remove debug_log module

src/app/methods/messages.rs

@@ -47,6 +47,7 @@ impl<T: TdClientTrait> MessageMethods<T> for App<T> {
         if let ChatState::MessageSelection { selected_index } = &mut self.chat_state {
             if *selected_index > 0 {
                 *selected_index -= 1;
+                self.stop_playback();
             }
         }
     }
@@ -59,9 +60,11 @@ impl<T: TdClientTrait> MessageMethods<T> for App<T> {
         if let ChatState::MessageSelection { selected_index } = &mut self.chat_state {
             if *selected_index < total - 1 {
                 *selected_index += 1;
+                self.stop_playback();
             } else {
                 // Дошли до самого нового сообщения - выходим из режима выбора
                 self.chat_state = ChatState::Normal;
+                self.stop_playback();
             }
         }
     }

src/app/mod.rs

@@ -100,6 +100,13 @@ pub struct App<T: TdClientTrait = TdClient> {
     /// Время последнего рендеринга изображений (для throttling до 15 FPS)
     #[cfg(feature = "images")]
     pub last_image_render_time: Option<std::time::Instant>,
+    // Voice playback
+    /// Аудиопроигрыватель для голосовых сообщений (rodio)
+    pub audio_player: Option<crate::audio::AudioPlayer>,
+    /// Кэш голосовых файлов (LRU, max 100 MB)
+    pub voice_cache: Option<crate::audio::VoiceCache>,
+    /// Состояние текущего воспроизведения
+    pub playback_state: Option<crate::tdlib::PlaybackState>,
 }
 
 impl<T: TdClientTrait> App<T> {
@@ -160,6 +167,10 @@ impl<T: TdClientTrait> App<T> {
             image_modal: None,
             #[cfg(feature = "images")]
             last_image_render_time: None,
+            // Voice playback
+            audio_player: crate::audio::AudioPlayer::new().ok(),
+            voice_cache: crate::audio::VoiceCache::new().ok(),
+            playback_state: None,
         }
     }
 
@@ -181,6 +192,15 @@ impl<T: TdClientTrait> App<T> {
         self.selected_chat_id.map(|id| id.as_i64())
     }
 
+    /// Останавливает воспроизведение голосового и сбрасывает состояние
+    pub fn stop_playback(&mut self) {
+        if let Some(ref player) = self.audio_player {
+            player.stop();
+        }
+        self.playback_state = None;
+        self.status_message = None;
+    }
+
     /// Get the selected chat info
     pub fn get_selected_chat(&self) -> Option<&ChatInfo> {
         self.selected_chat_id