feat(profile): "set your city" gamification box → one-time 500-coin reward

- New searchable city picker (src/lib/iran-cities.ts, ~60 Iranian cities,
  fa/en search) shown as a gold reward card at the top of the profile Basic tab.
- First time a non-empty city is set, the player earns 500 coins (CITY_REWARD),
  granted server-authoritatively. Collapses to a compact summary afterwards with
  a "change city" option (no re-reward).
- Frontend: UserProfile.city + cityRewardClaimed; mock-service grants on first
  set; session/service updateProfile accept `city`; celebratory toast + sfx.
- Backend (.NET): ProfileDto.City/CityRewardClaimed (JSON blob → no migration);
  ProfileService.Update grants +500 once and writes a "city" ledger entry.
- i18n: city.* keys (fa + en).

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

src/lib/online/mock-service.ts

@@ -6,6 +6,7 @@ import {
   ACHIEVEMENTS,
   CARD_BACKS,
   CARD_FRONTS,
+  CITY_REWARD,
   REACTION_PACKS,
   STICKER_PACKS,
   TITLES,
@@ -362,7 +363,13 @@ export class MockOnlineService implements OnlineService {
 
   async updateProfile(patch: Parameters<OnlineService["updateProfile"]>[0]) {
     const p = await this.getProfile();
-    this.profile = { ...p, ...patch };
+    const next = { ...p, ...patch };
+    // One-time reward: first time the player sets a (non-empty) city → +500 coins.
+    if (patch.city && patch.city.trim() && !p.cityRewardClaimed) {
+      next.coins = p.coins + CITY_REWARD;
+      next.cityRewardClaimed = true;
+    }
+    this.profile = next;
     this.saveProfile();
     return this.profile;
   }