@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)

backend/app/api/routes/coverage.py

@@ -11,6 +11,7 @@ from app.services.coverage_service import (
     CoveragePoint,
     apply_preset,
     PRESETS,
+    select_propagation_model,
 )
 from app.services.parallel_coverage_service import CancellationToken
 
@@ -58,6 +59,12 @@ async def calculate_coverage(request: CoverageRequest) -> CoverageResponse:
     effective_settings = apply_preset(request.settings.model_copy())
     models_used = _get_active_models(effective_settings)
 
+    # Add the selected propagation model for the first site's frequency
+    env = getattr(effective_settings, 'environment', 'urban')
+    primary_model = select_propagation_model(request.sites[0].frequency, env)
+    if primary_model.name not in models_used:
+        models_used.insert(0, primary_model.name)
+
     # Time the calculation
     start_time = time.time()
     cancel_token = CancellationToken()
@@ -182,7 +189,7 @@ async def get_buildings(
 
 def _get_active_models(settings: CoverageSettings) -> List[str]:
     """Determine which propagation models are active"""
-    models = ["okumura_hata"]  # Always active as base model
+    models = []  # Base propagation model added by caller via select_propagation_model()
 
     if settings.use_terrain:
         models.append("terrain_los")

backend/app/api/routes/system.py

@@ -46,15 +46,29 @@ async def get_system_info():
     }
 
 
+@router.get("/models")
+async def get_propagation_models():
+    """Return available propagation models and their valid ranges."""
+    from app.core.engine import engine
+    return {
+        "models": engine.get_available_models(),
+    }
+
+
 @router.post("/shutdown")
 async def shutdown():
-    """Graceful shutdown endpoint. Kills worker processes and exits."""
+    """Graceful shutdown endpoint. Kills worker processes then self-terminates.
+
+    Electron calls this first, waits briefly, then does PID-tree kill.
+    The os._exit(3s) is a safety net in case Electron doesn't kill us.
+    """
     from app.services.parallel_coverage_service import _kill_worker_processes
 
     killed = _kill_worker_processes()
 
-    # Schedule hard exit after response is sent
-    loop = asyncio.get_event_loop()
-    loop.call_later(0.5, lambda: os._exit(0))
+    # Safety net: self-terminate after 3s if Electron doesn't kill us.
+    # Delay is long enough for Electron to do PID-tree kill first (preferred).
+    loop = asyncio.get_running_loop()
+    loop.call_later(3.0, lambda: os._exit(0))
 
     return {"status": "shutting down", "workers_killed": killed}