Initial commit - Phase 3/4

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/backend/websocket/routes.py

@@ -0,0 +1,35 @@
+"""WebSocket endpoint routes."""
+from fastapi import APIRouter, WebSocket, WebSocketDisconnect
+from .manager import ws_manager
+
+router = APIRouter()
+
+
+@router.websocket("/events")
+async def websocket_endpoint(websocket: WebSocket):
+    """WebSocket endpoint for real-time event streaming.
+
+    Events include:
+    - connected: Initial connection confirmation
+    - system_stats: CPU, memory, temperature updates (every 5s)
+    - pm3_devices: Device list on connect/disconnect
+    - pm3_status: PM3 connection status changes
+    - ups_battery: Battery level updates
+    - ups_warning: Low battery warning
+    - ups_critical: Critical battery level
+    - ups_shutdown: Shutdown initiated
+    - ups_config_required: UPS needs configuration
+    - update_available: New version available
+    - update_downloading: Download progress
+    """
+    await ws_manager.connect(websocket)
+    try:
+        while True:
+            # Keep connection alive by waiting for messages or disconnect
+            # Client doesn't send data, but we need to detect disconnection
+            try:
+                await websocket.receive_text()
+            except WebSocketDisconnect:
+                break
+    finally:
+        await ws_manager.disconnect(websocket)