feat: soundboard, toast notifications, robust JSON parsing

Soundboard (Web Audio API):
- 8 ambient loops: rain, wind, fire, ocean, forest, tavern, thunder, cave
- 8 one-shot SFX: sword, bow, spell, door, coins, horn, dice, footsteps
- Brown noise generation for ambient textures
- Oscillator-based SFX with frequency sweeps
- Volume slider, active state indicators with pulsing dot
- Stop All button when ambients are playing
- Toast notifications on SFX trigger

Toast notification system:
- Zustand-based store with auto-dismiss (4s)
- 4 types: success, error, info, warning
- Slide-in animation from top-right
- Dismissible with × button
- Integrated into App shell

JSON parsing (all AI components):
- Shared lib/llm-parse.ts with extractJson, parseLlmJson, flattenValue, ensureArray
- Strips markdown code fences before parsing
- Handles nested objects where strings expected
- All 5 AI components use parseLlmJson instead of raw regex
- All prompts explicitly request raw JSON with no fences
- ItemForge shows raw response in <details> on parse failure

Full production build passing

src/index.css

@@ -179,4 +179,22 @@ body,
 *:focus-visible {
   outline: 2px solid var(--color-gold-bright);
   outline-offset: 2px;
+}
+
+/* ─── Animations ──────────────────────────────────────────────── */
+
+@keyframes slideIn {
+  from {
+    opacity: 0;
+    transform: translateX(1rem);
+  }
+  to {
+    opacity: 1;
+    transform: translateX(0);
+  }
+}
+
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
 }