Split card design into front+back, add sound effects & background music

Card design:
- Separate cardFront + cardBack (each own/equip independently)
- Fronts: classic (free), ivory/rosegold (buy), parchment/mint (earned)
- Backs: classic (free), sapphire/emerald (buy), ruby/royal (earned)
- PlayingCard `front` prop; table applies front to all faces, back to opponents
- Profile has front + back pickers; shop has both sections

Audio:
- Web Audio synth engine (no asset files): SFX for card/deal/trump/trick,
  win/lose, message, notify, award, levelup, purchase, kot + ambient music
- Toggles in profile (Audio) + mute button in game HUD; prefs persisted
- Wired across game-store, rewards, daily, shop, chat

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/i18n.tsx

@@ -224,6 +224,15 @@ const fa: Dict = {
 
   "reactions.title": "شکلک",
   "stickers.title": "استیکر",
+
+  "settings.audio": "تنظیمات صدا",
+  "settings.sound": "افکت صدا",
+  "settings.music": "موسیقی پس‌زمینه",
+
+  "profile.cardFront": "روی کارت",
+  "profile.cardBack": "پشت کارت",
+  "shop.cardfronts": "روی کارت‌ها",
+  "shop.cardbacks": "پشت کارت‌ها",
 };
 
 const en: Dict = {
@@ -437,6 +446,15 @@ const en: Dict = {
 
   "reactions.title": "Emoji",
   "stickers.title": "Stickers",
+
+  "settings.audio": "Audio",
+  "settings.sound": "Sound effects",
+  "settings.music": "Background music",
+
+  "profile.cardFront": "Card front",
+  "profile.cardBack": "Card back",
+  "shop.cardfronts": "Card fronts",
+  "shop.cardbacks": "Card backs",
 };
 
 const DICTS: Record<Locale, Dict> = { fa, en };