Implement complete search results + dual player UI

Backend Enhancements:
- Add ParsedMIDIInfo with track analysis and quality issues
- New /api/midi/parse endpoint for MIDI metadata extraction
- Enhanced MIDIService with parseMIDI method

MIDI Preview Player:
- Complete MIDIPlayer class with polyphonic playback
- Basic oscillator mapping (bass=square, mid=triangle, high=sine)
- Lookahead scheduling with proper cleanup
- Automatic stopping when MIDI ends

New UI Flow:
1. Search → Results table with metadata
2. Select MIDI → Shows parsed info (duration, tracks, tempo)
3. Dual transport: Preview Original vs Generate Motif
4. Try Next Result button for easy A/B testing

Search Results Table:
- Title, source, confidence bar, duration, track count
- Quality issues display (short duration, few notes, etc.)
- Auto-select best result, manual selection available
- Visual confidence bars and issue warnings

This makes the project feel "real" - you can now:
- See exactly what MIDI was found
- Verify it's the right song via preview
- Compare original vs procedural synthesis
- Easily try different results

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

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

server/src/server.ts

@@ -2,6 +2,7 @@ import express from 'express';
 import cors from 'cors';
 import { MIDISearchService } from './services/MIDISearchService.js';
 import { MIDIFetchService } from './services/MIDIFetchService.js';
+import { MIDIParseService } from './services/MIDIParseService.js';
 
 const app = express();
 const port = process.env.PORT || 3001;
@@ -11,6 +12,7 @@ app.use(express.json());
 
 const searchService = new MIDISearchService();
 const fetchService = new MIDIFetchService();
+const parseService = new MIDIParseService();
 
 // Search for MIDI files
 app.get('/api/midi/search', async (req, res) => {
@@ -53,6 +55,29 @@ app.get('/api/midi/fetch', async (req, res) => {
   }
 });
 
+// Parse MIDI metadata
+app.get('/api/midi/parse', async (req, res) => {
+  try {
+    const url = req.query.u as string;
+    if (!url) {
+      return res.status(400).json({ error: 'URL parameter "u" is required' });
+    }
+
+    console.log(`Parsing MIDI metadata: ${url}`);
+    const result = await fetchService.fetch(url);
+    
+    if (result.success && result.data) {
+      const metadata = parseService.parseMIDI(result.data);
+      res.json(metadata);
+    } else {
+      res.status(404).json({ error: result.error || 'Failed to fetch MIDI' });
+    }
+  } catch (error) {
+    console.error('Parse error:', error);
+    res.status(500).json({ error: 'Parse failed' });
+  }
+});
+
 // Health check
 app.get('/health', (req, res) => {
   res.json({ status: 'ok', timestamp: new Date().toISOString() });