feat: Rebuild as Court Manager Dashboard v2

- Complete rewrite for single Court Manager user
- Feature 1: Player Management (CRUD, ELO, skill level)
- Feature 2: Court Reservation (timeline, override)
- Feature 3: Match Event Builder (3-step wizard)
  - Step 1: Event setup with player selection + stage calculator
  - Step 2: Stage configurator (Open/Skill/RR/Tournament)
  - Step 3: Auto bracket generation
- Feature 4: Live Court View (main dashboard, 2x2 grid)
- Event Control: score entry, bracket advancement, court assignment
- Screen view: TV display per court (/screen/:id)
- Seed: 8 players, 4 courts, 1 completed + 1 active event
- Routes: / players courts events events/new events/:id screen/:id

backend/app/websocket_manager.py

@@ -0,0 +1,40 @@
+from typing import Dict, List
+from fastapi import WebSocket
+import json
+
+
+class ConnectionManager:
+    def __init__(self):
+        self.active_connections: Dict[str, List[WebSocket]] = {}
+
+    async def connect(self, websocket: WebSocket, channel: str):
+        await websocket.accept()
+        if channel not in self.active_connections:
+            self.active_connections[channel] = []
+        self.active_connections[channel].append(websocket)
+
+    def disconnect(self, websocket: WebSocket, channel: str):
+        if channel in self.active_connections:
+            try:
+                self.active_connections[channel].remove(websocket)
+            except ValueError:
+                pass
+
+    async def broadcast(self, channel: str, data: dict):
+        if channel not in self.active_connections:
+            return
+        dead = []
+        for ws in self.active_connections[channel]:
+            try:
+                await ws.send_json(data)
+            except Exception:
+                dead.append(ws)
+        for ws in dead:
+            self.disconnect(ws, channel)
+
+    async def broadcast_all(self, data: dict):
+        for channel in list(self.active_connections.keys()):
+            await self.broadcast(channel, data)
+
+
+manager = ConnectionManager()