Celebration animations for purchases, XP gains & achievement unlocks

- New global celebration system: celebration-store (queue) + CelebrationOverlay
  (animated: count-up XP, filling bar, level-up pop, achievement cards; plays
  levelUp/award sounds; tap or auto-dismiss). Rendered in page.tsx.
- Shop: every purchase now celebrates — XP packs animate XP gain + level-up,
  cosmetics show a "purchased!" pop. Newly-unlocked achievements (diffed from
  the profile before/after) animate too.
- XP purchases now actually evaluate achievements: gamification.evaluateAchievements
  (client) + Gamification.EvaluateAchievements (server, called in ShopBuy xp path)
  unlock level milestones + grant their coins.

Verified live: buying XP took L1→L5, unlocked level_5 server-side and credited its
reward. tsc + dotnet + next build clean; images rebuilt :1500/:1505.

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

src/lib/i18n.tsx

@@ -33,6 +33,7 @@ const fa: Dict = {
   "resume.cta": "بازگشت به بازی",
   "resume.matchEnded": "بازی به پایان رسید",
   "resume.matchEndedBody": "نتیجه و جایزه را ببینید",
+  "celebrate.purchased": "خرید با موفقیت انجام شد!",
 
   "achv.title": "دستاوردها",
   "achv.unlocked": "باز شده",
@@ -299,6 +300,7 @@ const en: Dict = {
   "resume.cta": "Return to game",
   "resume.matchEnded": "Match ended",
   "resume.matchEndedBody": "See the result and reward",
+  "celebrate.purchased": "Purchase complete!",
 
   "achv.title": "Achievements",
   "achv.unlocked": "Unlocked",