feat: Phase 3 — Workshop (community patch sharing)

Server:
- GET /api/v1/workshop — browse patches (search, tags, sort)
- POST /api/v1/workshop — share a patch (auth required)
- GET /api/v1/workshop/:id — single patch detail
- DELETE /api/v1/workshop/:id — soft delete (owner/admin)
- POST/DELETE /api/v1/workshop/:id/like — like/unlike
- POST /api/v1/workshop/:id/report — flag for moderation

Client:
- Workshop page with nav bar (Sandbox/SynthQuest/Workshop tabs)
- Search bar + tag filters (ambient, bass, drums, etc.)
- Sort by recent/popular
- Patch cards: title, author, tags, likes, module count
- "Cargar" button loads patch into Sandbox
- Share modal: title, description, tags, shares current canvas
- User badge + login button in Workshop nav
- Responsive: single column on mobile

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/client/src/main.jsx

@@ -2,19 +2,25 @@ import React, { useState } from 'react';
 import { createRoot } from 'react-dom/client';
 import App from './App';
 import GameApp from './game/GameApp.jsx';
+import Workshop from './components/Workshop.jsx';
 import { AuthProvider } from './services/AuthContext.jsx';
 import AuthModal from './components/AuthModal.jsx';
 import './index.css';
 
 function Root() {
-  const [mode, setMode] = useState('game'); // 'game' | 'sandbox'
+  const [mode, setMode] = useState('game'); // 'game' | 'sandbox' | 'workshop'
+
+  const nav = {
+    toGame: () => setMode('game'),
+    toSandbox: () => setMode('sandbox'),
+    toWorkshop: () => setMode('workshop'),
+  };
 
   return (
     <AuthProvider>
-      {mode === 'sandbox'
-        ? <App onSwitchToGame={() => setMode('game')} />
-        : <GameApp onSwitchToSandbox={() => setMode('sandbox')} />
-      }
+      {mode === 'sandbox' && <App onSwitchToGame={nav.toGame} onSwitchToWorkshop={nav.toWorkshop} />}
+      {mode === 'game' && <GameApp onSwitchToSandbox={nav.toSandbox} onSwitchToWorkshop={nav.toWorkshop} />}
+      {mode === 'workshop' && <Workshop onSwitchToSandbox={nav.toSandbox} onSwitchToGame={nav.toGame} />}
       <AuthModal />
     </AuthProvider>
   );