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/CityActionController.php

@@ -9,6 +9,7 @@ use App\Models\City;
 use App\Models\InventoryItem;
 use App\Models\Job;
 use App\Models\Transaction;
+use App\Support\Airports;
 use App\Support\Beach;
 use App\Support\CityPlazas;
 use App\Support\MissionTracker;
@@ -53,7 +54,15 @@ class CityActionController extends Controller
         // but never beyond the shoreline.
         $maxX = Beach::sandTo($city) + 2;
         $x = max((float) $city->bounds_min_x, min($maxX, (float) $data['pos_x']));
-        $z = max((float) $city->bounds_min_z, min((float) $city->bounds_max_z, (float) $data['pos_z']));
+        // Airport grounds (north/south strips) are walkable beyond the
+        // city bounds inside their X band.
+        $minZ = (float) $city->bounds_min_z;
+        $maxZ = (float) $city->bounds_max_z;
+        if (abs($x) <= Airports::VISIT_HALF_WIDTH) {
+            $minZ = Airports::VISIT_MIN_Z;
+            $maxZ = Airports::VISIT_MAX_Z;
+        }
+        $z = max($minZ, min($maxZ, (float) $data['pos_z']));
 
         $character->forceFill([
             'pos_x' => $x,