feat: implement Phase 11 — inline photo viewing with ratatui-image

Add feature-gated (`images`) inline photo support:
- New types: MediaInfo, PhotoInfo, PhotoDownloadState, ImagesConfig
- Media module: ImageCache (LRU filesystem cache), ImageRenderer (terminal protocol detection)
- Photo metadata extraction from TDLib MessagePhoto with download_file() API
- ViewImage command (v/м) to toggle photo expand/collapse in message selection
- Two-pass UI rendering: placeholder lines in message bubbles + StatefulImage overlay
- Collapse all expanded photos on Esc (exit selection mode)

Dependencies: ratatui-image 8.1, image 0.25 (optional, behind `images` feature flag)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/config/keybindings.rs

@@ -48,6 +48,9 @@ pub enum Command {
     ReactMessage,
     SelectMessage,
 
+    // Media
+    ViewImage,
+
     // Input
     SubmitMessage,
     Cancel,
@@ -201,7 +204,13 @@ impl Keybindings {
             KeyBinding::new(KeyCode::Char('у')), // RU
         ]);
         // Note: SelectMessage обрабатывается через Command::SubmitMessage в handle_enter_key()
-        
+
+        // Media
+        bindings.insert(Command::ViewImage, vec![
+            KeyBinding::new(KeyCode::Char('v')),
+            KeyBinding::new(KeyCode::Char('м')), // RU
+        ]);
+
         // Input
         bindings.insert(Command::SubmitMessage, vec![
             KeyBinding::new(KeyCode::Enter),