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>

scripts/sim.ts

@@ -89,12 +89,14 @@ function baseProfile(): UserProfile {
     },
     plan: "free",
     ownedAvatars: ["a-fox"],
-    ownedCardStyles: ["classic"],
+    ownedCardFronts: ["classic"],
+    ownedCardBacks: ["classic"],
     ownedTitles: ["novice"],
     ownedReactionPacks: [],
     ownedStickerPacks: [],
     title: "novice",
-    cardStyle: "classic",
+    cardFront: "classic",
+    cardBack: "classic",
     achievements: {},
     unlocked: [],
     createdAt: 0,