@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/tests/test_models/test_free_space.py

@@ -0,0 +1,82 @@
+"""
+Detailed unit tests for the Free Space Path Loss model.
+"""
+
+import sys
+import os
+import math
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..'))
+
+from app.propagation.base import PropagationInput
+from app.propagation.free_space import FreeSpaceModel
+
+
+def make_input(**kwargs) -> PropagationInput:
+    defaults = {
+        "frequency_mhz": 1800,
+        "distance_m": 1000,
+        "tx_height_m": 30,
+        "rx_height_m": 1.5,
+        "environment": "urban",
+    }
+    defaults.update(kwargs)
+    return PropagationInput(**defaults)
+
+
+class TestFreeSpaceModel:
+    def test_formula_accuracy(self):
+        """FSPL = 20*log10(d_km) + 20*log10(f_MHz) + 32.45"""
+        model = FreeSpaceModel()
+        # At 1km, 1000MHz: 20*0 + 20*60 + 32.45 = 92.45 dB
+        out = model.calculate(make_input(distance_m=1000, frequency_mhz=1000))
+        expected = 32.45 + 20 * math.log10(1.0) + 20 * math.log10(1000)
+        assert abs(out.path_loss_db - expected) < 0.1
+
+    def test_6db_per_distance_doubling(self):
+        model = FreeSpaceModel()
+        loss_1 = model.calculate(make_input(distance_m=1000)).path_loss_db
+        loss_2 = model.calculate(make_input(distance_m=2000)).path_loss_db
+        assert abs((loss_2 - loss_1) - 6.02) < 0.1
+
+    def test_6db_per_frequency_doubling(self):
+        model = FreeSpaceModel()
+        loss_1 = model.calculate(make_input(frequency_mhz=900)).path_loss_db
+        loss_2 = model.calculate(make_input(frequency_mhz=1800)).path_loss_db
+        assert abs((loss_2 - loss_1) - 6.02) < 0.1
+
+    def test_always_los(self):
+        model = FreeSpaceModel()
+        out = model.calculate(make_input())
+        assert out.is_los is True
+
+    def test_model_name(self):
+        model = FreeSpaceModel()
+        assert model.name == "Free-Space"
+
+    def test_wide_frequency_range(self):
+        model = FreeSpaceModel()
+        assert model.is_valid_for(make_input(frequency_mhz=1))
+        assert model.is_valid_for(make_input(frequency_mhz=100000))
+
+    def test_very_short_distance(self):
+        model = FreeSpaceModel()
+        out = model.calculate(make_input(distance_m=10))
+        assert out.path_loss_db > 0
+        assert out.path_loss_db < 80
+
+    def test_very_long_distance(self):
+        model = FreeSpaceModel()
+        out = model.calculate(make_input(distance_m=100000))
+        assert out.path_loss_db > 120
+
+
+if __name__ == "__main__":
+    instance = TestFreeSpaceModel()
+    for method_name in [m for m in dir(instance) if m.startswith("test_")]:
+        try:
+            getattr(instance, method_name)()
+            print(f"  PASS  {method_name}")
+        except Exception as e:
+            print(f"  FAIL  {method_name}: {e}")
+    print("\nAll tests completed.")