feat: admin mode, worlds 4-6, and stereo output fix

- Admin panel: add/remove stars, unlock worlds, reset progress (🛠 button)
- World 4 "Modulación" (8 levels): vibrato, sirena, wah-wah, auto-pan, FM, wobble bass
- World 5 "Efectos" (8 levels): delay, slapback, reverb, distortion, dub echo, shoegaze, ambient
- World 6 "Diseño Sonoro" (8 levels): kick, hi-hat, snare, pad, reese bass, laser, trance arp, final boss
- Star unlock progression: W4=36★, W5=48★, W6=60★ (total 48 levels, 144 stars)
- Fix stereo output: left/right channels now route through Tone.Merge for true stereo separation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/game/GameApp.jsx

@@ -1,17 +1,22 @@
 import React, { useState, useCallback } from 'react';
 import WorldMap from './WorldMap.jsx';
 import PuzzleView from './PuzzleView.jsx';
+import AdminPanel from './AdminPanel.jsx';
 import { WORLD_1 } from './levels/world1.js';
 import { WORLD_2 } from './levels/world2.js';
 import { WORLD_3 } from './levels/world3.js';
+import { WORLD_4 } from './levels/world4.js';
+import { WORLD_5 } from './levels/world5.js';
+import { WORLD_6 } from './levels/world6.js';
 
-const allWorlds = [WORLD_1, WORLD_2, WORLD_3];
+const allWorlds = [WORLD_1, WORLD_2, WORLD_3, WORLD_4, WORLD_5, WORLD_6];
 
 export default function GameApp({ onSwitchToSandbox }) {
   const [view, setView] = useState('map');
   const [currentLevel, setCurrentLevel] = useState(null);
   const [currentLevelIndex, setCurrentLevelIndex] = useState(0);
   const [currentWorld, setCurrentWorld] = useState(null);
+  const [showAdmin, setShowAdmin] = useState(false);
 
   const handleSelectLevel = useCallback((level, world) => {
     const idx = world.levels.findIndex(l => l.id === level.id);
@@ -61,9 +66,18 @@ export default function GameApp({ onSwitchToSandbox }) {
   }
 
   return (
-    <WorldMap
-      onSelectLevel={handleSelectLevel}
-      onSandbox={onSwitchToSandbox}
-    />
+    <>
+      <WorldMap
+        onSelectLevel={handleSelectLevel}
+        onSandbox={onSwitchToSandbox}
+        onAdmin={() => setShowAdmin(true)}
+      />
+      {showAdmin && (
+        <AdminPanel
+          worlds={allWorlds}
+          onClose={() => setShowAdmin(false)}
+        />
+      )}
+    </>
   );
 }