Add Week 3 polish and late-game features

VC funding system (seed through IPO with requirements gating), 15
achievements with engine checker, model tuning presets and unlockable
sliders, overload policy controls, open-source mechanic with reputation
boost, enhanced Recharts analytics (subscriber/reputation/revenue vs
expenses charts), M&A acquisition system, sidebar NEW badges on era
transitions, tutorial hints, and wired-up settings toggles.

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

apps/web/src/pages/SettingsPage.tsx

@@ -4,8 +4,17 @@ import { useGameStore } from '@/store';
 export function SettingsPage() {
   const settings = useGameStore((s) => s.meta.settings);
   const companyName = useGameStore((s) => s.meta.companyName);
+  const updateState = useGameStore((s) => s.updateState);
   const fileInputRef = useRef<HTMLInputElement>(null);
 
+  const toggleSound = () => {
+    updateState({ meta: { ...useGameStore.getState().meta, settings: { ...settings, soundEnabled: !settings.soundEnabled } } });
+  };
+
+  const setMusicVolume = (v: number) => {
+    updateState({ meta: { ...useGameStore.getState().meta, settings: { ...settings, musicVolume: v } } });
+  };
+
   const handleReset = () => {
     if (confirm('Are you sure you want to reset all progress? This cannot be undone.')) {
       localStorage.removeItem('ai-tycoon-save');
@@ -62,15 +71,22 @@ export function SettingsPage() {
             <div className="text-sm">Sound Effects</div>
             <div className="text-xs text-surface-400">Play UI sounds and notifications</div>
           </div>
-          <ToggleSwitch checked={settings.soundEnabled} onChange={() => {}} />
+          <ToggleSwitch checked={settings.soundEnabled} onChange={toggleSound} />
         </div>
 
         <div className="flex items-center justify-between">
           <div>
-            <div className="text-sm">Music</div>
-            <div className="text-xs text-surface-400">Background music (coming soon)</div>
+            <div className="text-sm">Music Volume</div>
+            <div className="text-xs text-surface-400">Background music level</div>
           </div>
-          <ToggleSwitch checked={settings.soundEnabled} onChange={() => {}} />
+          <input
+            type="range"
+            min={0}
+            max={100}
+            value={settings.musicVolume * 100}
+            onChange={(e) => setMusicVolume(Number(e.target.value) / 100)}
+            className="w-32 accent-accent"
+          />
         </div>
       </div>