@mytec: feat: Phase 3.0 Architecture Refactor ✅

Major refactoring of RFCP backend:
- Modular propagation models (8 models)
- SharedMemoryManager for terrain data
- ProcessPoolExecutor parallel processing
- WebSocket progress streaming
- Building filtering pipeline (351k → 15k)
- 82 unit tests

Performance: Standard preset 38s → 5s (7.6x speedup)

Known issue: Detailed preset timeout (fix in 3.1.0)

frontend/src/hooks/useWebSocket.ts

@@ -0,0 +1,30 @@
+/**
+ * React hook wrapping the WebSocket singleton service.
+ *
+ * Provides reactive connection state and progress for UI components.
+ * The actual WS connection is managed by wsService singleton so it
+ * persists across component remounts.
+ *
+ * Usage:
+ *   const { connected, progress } = useWebSocket();
+ */
+
+import { useEffect, useState } from 'react';
+import { wsService } from '@/services/websocket.ts';
+import { useCoverageStore } from '@/store/coverage.ts';
+
+export function useWebSocket() {
+  const [connected, setConnected] = useState(wsService.connected);
+  const progress = useCoverageStore((s) => s.progress);
+
+  useEffect(() => {
+    // Connect the singleton if not already connected
+    wsService.connect();
+
+    // Subscribe to connection state changes
+    const unsub = wsService.onConnectionChange(setConnected);
+    return unsub;
+  }, []);
+
+  return { connected, progress };
+}