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/online/gamification.ts

@@ -298,6 +298,40 @@ export function achievementById(id: string): AchievementDef | undefined {
   return ACHIEVEMENTS.find((a) => a.id === id);
 }
 
+/**
+ * Re-evaluate all achievements against the profile's current state (used outside
+ * matches, e.g. after an XP-pack purchase crosses a level milestone). Unlocks new
+ * ones, grants their coin rewards, and returns the newly-unlocked list.
+ */
+export function evaluateAchievements(profile: UserProfile): {
+  profile: UserProfile;
+  newAchievements: AchievementUnlock[];
+} {
+  const achievements = { ...profile.achievements };
+  const unlocked = [...profile.unlocked];
+  const newAchievements: AchievementUnlock[] = [];
+  let coins = 0;
+  for (const def of ACHIEVEMENTS) {
+    const prog = achievementProgress(def, profile.stats, profile.rating, profile.level);
+    achievements[def.id] = prog;
+    if (prog >= def.goal && !unlocked.includes(def.id)) {
+      unlocked.push(def.id);
+      coins += def.coinReward;
+      newAchievements.push({
+        id: def.id,
+        nameFa: def.nameFa,
+        nameEn: def.nameEn,
+        icon: def.icon,
+        coinReward: def.coinReward,
+      });
+    }
+  }
+  return {
+    profile: { ...profile, achievements, unlocked, coins: profile.coins + coins },
+    newAchievements,
+  };
+}
+
 /** The sticker pack (if any) that unlocking this achievement grants. */
 export function stickerPackForAchievement(achId: string): StickerPackDef | undefined {
   return STICKER_PACKS.find((p) => p.unlockAchievement === achId);