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>

src/services/MIDIService.ts

@@ -0,0 +1,61 @@
+interface MIDISearchResult {
+  id: string;
+  title: string;
+  source: string;
+  pageUrl: string;
+  midiUrl: string;
+  confidence: number;
+}
+
+interface MIDISearchResponse {
+  results: MIDISearchResult[];
+  count: number;
+}
+
+export class MIDIService {
+  private baseUrl: string;
+
+  constructor(baseUrl = 'http://localhost:3001') {
+    this.baseUrl = baseUrl;
+  }
+
+  async search(query: string): Promise<MIDISearchResult[]> {
+    try {
+      const response = await fetch(`${this.baseUrl}/api/midi/search?q=${encodeURIComponent(query)}`);
+      
+      if (!response.ok) {
+        throw new Error(`Search failed: ${response.status}`);
+      }
+
+      const data: MIDISearchResponse = await response.json();
+      return data.results;
+    } catch (error) {
+      console.error('MIDI search error:', error);
+      return [];
+    }
+  }
+
+  async fetchMIDI(url: string): Promise<ArrayBuffer | null> {
+    try {
+      const response = await fetch(`${this.baseUrl}/api/midi/fetch?u=${encodeURIComponent(url)}`);
+      
+      if (!response.ok) {
+        throw new Error(`Fetch failed: ${response.status}`);
+      }
+
+      return await response.arrayBuffer();
+    } catch (error) {
+      console.error('MIDI fetch error:', error);
+      return null;
+    }
+  }
+
+  async checkHealth(): Promise<boolean> {
+    try {
+      const response = await fetch(`${this.baseUrl}/health`);
+      return response.ok;
+    } catch {
+      return false;
+    }
+  }
+}