100 gated gifts (level/rating-locked) + requirement system

Adds ~100 new purchasable gifts that are LOCKED until a level/rating gate is met,
then buyable with coins — value scales with the gate:
- 45 gift avatars (types.ts), 35 gift titles + 20 gift card backs (gamification.ts),
  all reusing existing renderers. Tier (1-5) encoded in the id (-t<n>-).
- Gate model: GIFT_TIERS (shared) → reqLevel/reqRating on AvatarDef/TitleDef/
  CardBackDef + ShopItem. Tiers: t1 free, t2 Lv10, t3 Lv20, t4 Lv35, t5 Rating1700.
- Shop UI: locked cards dim + show the requirement (Lock + "Level 20"), buy
  disabled until met; mock buyItem enforces it offline.
- Server enforces generically — ProfileService parses the tier from the id and
  checks the player's level/rating (no 100-entry mirror). Mirrors GIFT_TIERS.
- i18n shop.reqLevel/reqRating (fa+en).

Verified: tsc + sim + next build + dotnet build all pass.

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

src/lib/i18n.tsx

@@ -310,6 +310,8 @@ const fa: Dict = {
   "shop.xp": "امتیاز تجربه (XP)",
   "shop.xpHint": "افزایش سریع سطح — XP گران است",
   "shop.includes": "شامل",
+  "shop.reqLevel": "سطح",
+  "shop.reqRating": "امتیاز",
   "reward.newTitle": "عنوان جدید",
 
   "reactions.title": "شکلک",
@@ -640,6 +642,8 @@ const en: Dict = {
   "shop.xp": "XP packs",
   "shop.xpHint": "Level up faster — XP is expensive",
   "shop.includes": "Includes",
+  "shop.reqLevel": "Level",
+  "shop.reqRating": "Rating",
   "reward.newTitle": "New title",
 
   "reactions.title": "Emoji",