feat: complete Phase 13 - Keyboard Shortcuts

Added all remaining keyboard shortcuts for a complete keyboard-driven workflow:

Playback Shortcuts:
- Home: Jump to start
- End: Jump to end
- Left/Right Arrow: Seek ±1 second
- Ctrl+Left/Right: Seek ±5 seconds

Editing Shortcuts:
- Ctrl+A: Select All (entire track content)

View Shortcuts:
- Ctrl+Plus/Equals: Zoom in
- Ctrl+Minus: Zoom out
- Ctrl+0: Fit to view

All shortcuts work seamlessly with existing shortcuts:
- Spacebar: Play/Pause
- Ctrl+Z/Y: Undo/Redo
- Ctrl+X/C/V: Cut/Copy/Paste
- Ctrl+S: Save
- Ctrl+D: Duplicate
- Delete/Backspace: Delete
- Escape: Clear selection

The editor is now fully controllable via keyboard for a professional
audio editing workflow similar to Audacity/Reaper.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

components/editor/AudioEditor.tsx

@@ -1386,12 +1386,90 @@ export function AudioEditor() {
       if (e.key === 'Escape') {
         e.preventDefault();
         setSelectedTrackId(null);
+        return;
+      }
+
+      // Home: Go to start
+      if (e.key === 'Home') {
+        e.preventDefault();
+        seek(0);
+        return;
+      }
+
+      // End: Go to end
+      if (e.key === 'End') {
+        e.preventDefault();
+        seek(duration);
+        return;
+      }
+
+      // Left Arrow: Seek backward 1 second
+      if (e.key === 'ArrowLeft' && !e.ctrlKey && !e.metaKey) {
+        e.preventDefault();
+        seek(Math.max(0, currentTime - 1));
+        return;
+      }
+
+      // Right Arrow: Seek forward 1 second
+      if (e.key === 'ArrowRight' && !e.ctrlKey && !e.metaKey) {
+        e.preventDefault();
+        seek(Math.min(duration, currentTime + 1));
+        return;
+      }
+
+      // Ctrl+Left Arrow: Seek backward 5 seconds
+      if (e.key === 'ArrowLeft' && (e.ctrlKey || e.metaKey)) {
+        e.preventDefault();
+        seek(Math.max(0, currentTime - 5));
+        return;
+      }
+
+      // Ctrl+Right Arrow: Seek forward 5 seconds
+      if (e.key === 'ArrowRight' && (e.ctrlKey || e.metaKey)) {
+        e.preventDefault();
+        seek(Math.min(duration, currentTime + 5));
+        return;
+      }
+
+      // Ctrl+A: Select All (select all content on current track)
+      if ((e.ctrlKey || e.metaKey) && e.key === 'a') {
+        e.preventDefault();
+        if (selectedTrackId) {
+          const track = tracks.find(t => t.id === selectedTrackId);
+          if (track?.audioBuffer) {
+            updateTrack(selectedTrackId, {
+              selection: { start: 0, end: track.audioBuffer.duration }
+            });
+          }
+        }
+        return;
+      }
+
+      // Ctrl+Plus/Equals: Zoom in
+      if ((e.ctrlKey || e.metaKey) && (e.key === '+' || e.key === '=')) {
+        e.preventDefault();
+        handleZoomIn();
+        return;
+      }
+
+      // Ctrl+Minus: Zoom out
+      if ((e.ctrlKey || e.metaKey) && e.key === '-') {
+        e.preventDefault();
+        handleZoomOut();
+        return;
+      }
+
+      // Ctrl+0: Fit to view
+      if ((e.ctrlKey || e.metaKey) && e.key === '0') {
+        e.preventDefault();
+        handleFitToView();
+        return;
       }
     };
 
     window.addEventListener('keydown', handleKeyDown);
     return () => window.removeEventListener('keydown', handleKeyDown);
-  }, [togglePlayPause, canUndo, canRedo, undo, redo, handleCut, handleCopy, handlePaste, handleDelete, handleDuplicate, handleSaveProject]);
+  }, [togglePlayPause, canUndo, canRedo, undo, redo, handleCut, handleCopy, handlePaste, handleDelete, handleDuplicate, handleSaveProject, seek, duration, currentTime, selectedTrackId, tracks, updateTrack, handleZoomIn, handleZoomOut, handleFitToView]);
 
   return (
     <>