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/config/keybindings.rs

@@ -49,7 +49,12 @@ pub enum Command {
     SelectMessage,
 
     // Media
-    ViewImage,
+    ViewImage,       // v - просмотр фото
+
+    // Voice playback
+    TogglePlayback,  // Space - play/pause
+    SeekForward,     // → - seek +5s
+    SeekBackward,    // ← - seek -5s
 
     // Input
     SubmitMessage,
@@ -211,6 +216,17 @@ impl Keybindings {
             KeyBinding::new(KeyCode::Char('м')), // RU
         ]);
 
+        // Voice playback
+        bindings.insert(Command::TogglePlayback, vec![
+            KeyBinding::new(KeyCode::Char(' ')),
+        ]);
+        bindings.insert(Command::SeekForward, vec![
+            KeyBinding::new(KeyCode::Right),
+        ]);
+        bindings.insert(Command::SeekBackward, vec![
+            KeyBinding::new(KeyCode::Left),
+        ]);
+
         // Input
         bindings.insert(Command::SubmitMessage, vec![
             KeyBinding::new(KeyCode::Enter),