feat: 5 categorías rotativas por partida + pool de 200 preguntas + mejoras UI

Cambios principales:
- Tablero ahora muestra 5 categorías aleatorias (de 8 disponibles)
- Pool de 200 preguntas (8 cats × 5 diffs × 5 opciones)
- Preguntas rotan aleatoriamente entre partidas
- Diseño mejorado estilo Jeopardy con efectos visuales
- Socket singleton para conexión persistente
- Nuevos sonidos: game_start, player_join, question_reveal, hover, countdown
- Control de volumen vertical
- Barra de progreso del timer en modal de preguntas
- Animaciones mejoradas con Framer Motion

Backend:
- question_service: selección aleatoria de 5 categorías
- room_manager: fix retorno de create_room
- game_events: carga board desde DB, await en enter_room

Frontend:
- Game.tsx: tablero dinámico, efectos hover, mejor scoreboard
- useSocket: singleton service, eventos con sonidos
- SoundControl: slider vertical
- soundStore: 5 nuevos efectos de sonido

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

backend/app/services/question_service.py

@@ -1,11 +1,15 @@
 from typing import Optional, List, Dict
 from datetime import date
-from sqlalchemy import select, and_
+import random
+from sqlalchemy import select, and_, func
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.models.question import Question
 from app.models.category import Category
 
+# Number of categories per game
+CATEGORIES_PER_GAME = 5
+
 
 class QuestionService:
     async def get_daily_questions(
@@ -64,16 +68,49 @@ class QuestionService:
         target_date: Optional[date] = None
     ) -> Dict[str, List[dict]]:
         """
-        Genera el tablero 8×5 para el juego.
-        Si no hay suficientes preguntas, retorna lo disponible.
+        Genera el tablero 5×5 para el juego.
+        Selecciona 5 categorías aleatorias y 1 pregunta por dificultad.
 
         Returns:
             Dict con category_id como string (para JSON) -> lista de preguntas
         """
-        board = await self.get_daily_questions(db, target_date)
+        full_board = await self.get_daily_questions(db, target_date)
 
-        # Convertir keys a string para JSON
-        return {str(k): v for k, v in board.items()}
+        if not full_board:
+            return {}
+
+        # Get available category IDs that have questions
+        available_categories = list(full_board.keys())
+
+        # Select random categories (up to CATEGORIES_PER_GAME)
+        num_categories = min(CATEGORIES_PER_GAME, len(available_categories))
+        selected_categories = random.sample(available_categories, num_categories)
+
+        # Build the game board with selected categories
+        game_board: Dict[str, List[dict]] = {}
+
+        for cat_id in selected_categories:
+            questions_by_difficulty: Dict[int, List[dict]] = {}
+
+            # Group questions by difficulty
+            for q in full_board[cat_id]:
+                diff = q["difficulty"]
+                if diff not in questions_by_difficulty:
+                    questions_by_difficulty[diff] = []
+                questions_by_difficulty[diff].append(q)
+
+            # Select one random question per difficulty
+            selected_questions = []
+            for difficulty in range(1, 6):  # 1-5
+                if difficulty in questions_by_difficulty:
+                    questions = questions_by_difficulty[difficulty]
+                    selected_q = random.choice(questions)
+                    selected_questions.append(selected_q)
+
+            if selected_questions:
+                game_board[str(cat_id)] = selected_questions
+
+        return game_board
 
     async def get_question_by_id(
         self,

backend/app/services/room_manager.py

@@ -59,9 +59,9 @@ class RoomManager:
         )
 
         # Add player to room
-        await self.add_player(room_code, player_name, "A", socket_id)
+        room = await self.add_player(room_code, player_name, "A", socket_id)
 
-        return room_state
+        return room
 
     async def get_room(self, room_code: str) -> Optional[dict]:
         """Get room state by code."""