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/src/utils/ScoreUtils.ts

@@ -0,0 +1,109 @@
+export class ScoreUtils {
+  static calculateConfidence(title: string, query: string, source: string): number {
+    const titleLower = title.toLowerCase();
+    const queryLower = query.toLowerCase();
+    
+    let score = 0;
+    
+    // Token matching - split and check individual words
+    const titleTokens = this.tokenize(titleLower);
+    const queryTokens = this.tokenize(queryLower);
+    
+    // Exact title match gets high score
+    if (titleLower.includes(queryLower)) {
+      score += 0.8;
+    }
+    
+    // Token overlap scoring
+    const matchingTokens = queryTokens.filter(token => 
+      titleTokens.some(titleToken => 
+        titleToken.includes(token) || token.includes(titleToken)
+      )
+    );
+    
+    const tokenMatchRatio = matchingTokens.length / queryTokens.length;
+    score += tokenMatchRatio * 0.6;
+    
+    // Penalty for low-quality indicators
+    const penalties = [
+      { pattern: /karaoke|kar|midkar/, penalty: 0.3 },
+      { pattern: /vocal|lyrics/, penalty: 0.2 },
+      { pattern: /demo|test|sample/, penalty: 0.2 },
+      { pattern: /incomplete|broken/, penalty: 0.5 },
+    ];
+    
+    for (const { pattern, penalty } of penalties) {
+      if (pattern.test(titleLower)) {
+        score -= penalty;
+      }
+    }
+    
+    // Bonus for direct .mid links
+    if (title.includes('.mid')) {
+      score += 0.1;
+    }
+    
+    // Source-specific scoring adjustments
+    if (source === 'bitmidi') {
+      score += 0.1; // Slight preference for BitMidi (more curated)
+    }
+    
+    // Ensure score is between 0 and 1
+    return Math.max(0, Math.min(1, score));
+  }
+  
+  static assessQuality(buffer: ArrayBuffer): { 
+    score: number; 
+    duration?: number; 
+    trackCount?: number; 
+    issues: string[] 
+  } {
+    const issues: string[] = [];
+    let score = 0.5; // Base score
+    
+    // File size checks
+    const size = buffer.byteLength;
+    if (size < 1000) {
+      issues.push('File too small');
+      score -= 0.3;
+    } else if (size > 5_000_000) {
+      issues.push('File very large');
+      score -= 0.1;
+    } else {
+      score += 0.1; // Good size range
+    }
+    
+    // Basic MIDI header validation
+    const view = new Uint8Array(buffer);
+    const header = String.fromCharCode(...view.slice(0, 4));
+    
+    if (header !== 'MThd') {
+      issues.push('Invalid MIDI header');
+      score -= 0.5;
+    } else {
+      score += 0.2;
+    }
+    
+    // TODO: More sophisticated parsing for duration, tempo changes, track count
+    // For MVP, we'll do basic heuristics
+    
+    return {
+      score: Math.max(0, Math.min(1, score)),
+      issues
+    };
+  }
+  
+  private static tokenize(text: string): string[] {
+    return text
+      .toLowerCase()
+      .replace(/[^\w\s]/g, ' ') // Remove punctuation
+      .split(/\s+/)
+      .filter(token => token.length > 1) // Remove single characters
+      .filter(token => !this.isStopWord(token));
+  }
+  
+  private static isStopWord(word: string): boolean {
+    const stopWords = ['the', 'and', 'or', 'but', 'in', 'on', 'at', 'to', 'for', 'of', 'with', 'by'];
+    return stopWords.includes(word);
+  }
+}