feat(city): add plaza exercise system with health tracking

- Adds CityPlazas support class for deterministic public plaza generation with outdoor gym equipment
- Implements exercise and stop-exercise actions with proximity validation to equipment
- Introduces health (0-100) and exercise_count attributes to Character model
- Reduces hospital stay duration from two game days to one game hour
- Adds 3D gym equipment rendering (bench, bars, bike, treadmill) in city viewer
- Includes exercise state machine handling in world ticker with energy drain
- Adds comprehensive PlazaExerciseTest and updates HospitalAdmissionTest
- Provides localized UI strings for health HUD and exercise prompts

lang/es.json

@@ -192,7 +192,7 @@
     "city.citizens_near": "Ciudadanos",
     "city.apply_job": "Solicitar",
     "city.buy_hint": "Compra 1 comida + 1 agua + 10 materiales",
-    "city.hospital_hit": "¡Te atropelló un vehículo! Internado en el hospital por 2 días.",
+    "city.hospital_hit": "¡Te atropelló un vehículo! Internado en el hospital por 1 hora.",
     "city.hospital_already": "Ya está internado en el hospital.",
     "city.hospital_blocked": "Está internado y no puede hacer eso ahora.",
     "city.hospital_bed": "Internado en el hospital",
@@ -204,5 +204,17 @@
     "city.vol_music": "Música",
     "city.vol_sfx": "Efectos",
     "city.mute": "Silenciar",
-    "city.audio_hint": "Volumen guardado en este dispositivo."
+    "city.audio_hint": "Volumen guardado en este dispositivo.",
+    "city.hud_health": "Salud",
+    "city.hud_exercise": "Ejercicios",
+    "city.exercise_use": "Pulse E para ejercitarse",
+    "city.exercise_active": "Ejercitándose",
+    "city.exercise_stopHint": "para parar",
+    "city.exercise_ok": "¡Bien! +2 de salud.",
+    "city.exercise_need_equipment": "Acérquese a un equipo de la plaza.",
+    "city.exercise_need_awake": "Debe estar despierto para ejercitarse.",
+    "city.exercise_tired": "Está demasiado cansado para ejercitarse.",
+    "city.exercise_max_health": "¡La salud ya está en el máximo!",
+    "city.exerciseStart": "Empezando a ejercitarse…",
+    "city.exerciseStop": "Ejercicio terminado."
 }