Add complete MIDI search and synthesis pipeline

Backend (MVP):
- Express API with /search and /fetch endpoints
- BitMidi and Dongrays search adapters with scoring heuristics
- CORS proxy with disk caching and validation
- Quality assessment and file size limits

Frontend Integration:
- Switch to @tonejs/midi parser for reliable MIDI parsing
- MIDIService for backend API communication
- MotifEngine updated to try real MIDI, fallback to synthetic
- Enhanced error handling and logging

Development:
- Concurrent frontend/backend npm scripts
- Basic project documentation

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

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

package.json

@@ -5,7 +5,10 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
+    "dev:backend": "cd server && npm run dev",
+    "dev:all": "npm run dev:backend & npm run dev",
     "build": "tsc && vite build",
+    "build:backend": "cd server && npm run build",
     "preview": "vite preview",
     "lint": "eslint src --ext .ts,.tsx",
     "typecheck": "tsc --noEmit"
@@ -19,7 +22,7 @@
     "vite": "^5.0.0"
   },
   "dependencies": {
-    "midi-parser-js": "^4.0.4"
+    "@tonejs/midi": "^2.0.28"
   },
   "keywords": [
     "web-audio",