feat: implement Phase 12.2 - Project Management UI Integration

Integrated complete project management system with auto-save:

**AudioEditor.tsx - Full Integration:**
- Added "Projects" button in header toolbar (FolderOpen icon)
- Project state management (currentProjectId, currentProjectName, projects list)
- Comprehensive project handlers:
  - `handleOpenProjectsDialog` - Opens dialog and loads project list
  - `handleSaveProject` - Saves current project to IndexedDB
  - `handleNewProject` - Creates new project with confirmation
  - `handleLoadProject` - Loads project and restores all tracks/settings
  - `handleDeleteProject` - Deletes project with cleanup
  - `handleDuplicateProject` - Creates project copy
- Auto-save effect: Saves project every 30 seconds when tracks exist
- ProjectsDialog component integrated with all handlers
- Toast notifications for all operations

**lib/storage/projects.ts:**
- Re-exported ProjectMetadata type for easier importing
- Fixed type exports

**Key Features:**
- **Auto-save**: Automatically saves every 30 seconds
- **Project persistence**: Full track state, audio buffers, effects, automation
- **Smart loading**: Restores zoom, track order, and all track properties
- **Safety confirmations**: Warns before creating new project with unsaved changes
- **User feedback**: Toast messages for all operations (save, load, delete, duplicate)
- **Seamless workflow**: Projects → Import → Export in logical toolbar order

**User Flow:**
1. Click "Projects" to open project manager
2. Create new project or load existing
3. Work on tracks (auto-saves every 30s)
4. Switch between projects anytime
5. Duplicate projects for experimentation
6. Delete old projects to clean up

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

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

lib/storage/projects.ts

@@ -11,12 +11,15 @@ import {
   serializeAudioBuffer,
   deserializeAudioBuffer,
   type ProjectData,
-  type ProjectMetadata,
   type SerializedTrack,
 } from './db';
+import type { ProjectMetadata } from './db';
 import { getAudioContext } from '../audio/context';
 import { generateId } from '../audio/effects/chain';
 
+// Re-export ProjectMetadata for easier importing
+export type { ProjectMetadata } from './db';
+
 /**
  * Generate unique project ID
  */