feat(city): add airports, ATC agent, luminous signs, and AI model fallback chain

- Add two airports (north/south) with full geometry: runways, taxiways,
  aprons, terminals, hangars, stands, and helipads; walkable airport
  grounds extend beyond city bounds.
- Introduce ATC AI agent ("Torre de Controle City10") using AI_ATC_MODEL
  to generate takeoff clearances; includes dispatch endpoint with
  30-second cooldown and deterministic fallback on failure.
- Implement AI model fallback chain: preferred model → AI_FALLBACK_MODEL
  before failing, applied in ChatController and PersonTalkController.
- Add luminous sign labels (letreiros) for plazas, beach, food, hospital,
  school, city hall, and airports with day/night glow.
- Fix city presence cache: compute is_me per viewer instead of baking
  into shared per-second cache to prevent cross-user flag leakage.
- Add tests: AirportTest, CityPresenceTest, SignLabelsTest, and
  PersonTalkTest fallback model retry scenario.

app/Http/Controllers/Web/CityPresenceController.php

@@ -35,8 +35,12 @@ class CityPresenceController extends Controller
                 ->first() ?? $city;
         }
 
+        // Rows are shared across users for one second, so is_me must NOT
+        // be baked into the cached payload — it is computed per viewer
+        // below (otherwise user B sees user A's is_me flags and could see
+        // their own character as a remote citizen).
         $cacheKey = 'presence.'.$city->id.'.'.now()->timestamp;
-        $citizens = Cache::remember($cacheKey, 1, function () use ($city, $me) {
+        $citizens = Cache::remember($cacheKey, 1, function () use ($city) {
             return Character::query()
                 ->where('city_id', $city->id)
                 ->where(function ($q): void {
@@ -52,13 +56,18 @@ class CityPresenceController extends Controller
                     'status' => $c->state,
                     'position' => [(float) $c->pos_x, (float) $c->pos_y, (float) $c->pos_z],
                     'is_online' => (bool) $c->is_online,
-                    'is_me' => (int) $c->id === (int) $me->id,
                     'owner_name' => $c->user?->name,
                 ])
                 ->values()
                 ->all();
         });
 
+        $viewerId = (int) $me->id;
+        $citizens = array_map(
+            static fn (array $c): array => $c + ['is_me' => (int) $c['id'] === $viewerId],
+            $citizens
+        );
+
         return response()->json([
             'city_id' => $city->id,
             'server_time' => now()->toIso8601String(),