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>

server/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "motif-backend",
+  "version": "0.1.0",
+  "description": "MIDI search and proxy backend for Motif",
+  "type": "module",
+  "main": "dist/server.js",
+  "scripts": {
+    "dev": "tsx watch src/server.ts",
+    "build": "tsc",
+    "start": "node dist/server.js"
+  },
+  "dependencies": {
+    "express": "^4.18.2",
+    "cors": "^2.8.5",
+    "cheerio": "^1.0.0-rc.12",
+    "crypto": "^1.0.1"
+  },
+  "devDependencies": {
+    "@types/express": "^4.17.21",
+    "@types/cors": "^2.8.17",
+    "@types/node": "^20.0.0",
+    "tsx": "^4.0.0",
+    "typescript": "^5.0.0"
+  }
+}