@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_geometry/test_intersection.py

@@ -0,0 +1,77 @@
+"""
+Unit tests for line-segment intersection calculations.
+
+These require NumPy, so use __main__ block with conditional import.
+"""
+
+import sys
+import os
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', '..'))
+
+import numpy as np
+from app.geometry.intersection import line_segments_intersect_batch
+
+
+class TestLineSegmentIntersect:
+    def test_crossing_lines(self):
+        """Two crossing segments should intersect."""
+        # Line from (0,0)→(1,1) and (0,1)→(1,0)
+        result = line_segments_intersect_batch(
+            p1=np.array([0.0, 0.0]),
+            p2=np.array([1.0, 1.0]),
+            seg_starts=np.array([[0.0, 1.0]]),
+            seg_ends=np.array([[1.0, 0.0]]),
+        )
+        assert result[0] == True
+
+    def test_parallel_lines(self):
+        """Parallel lines should not intersect."""
+        result = line_segments_intersect_batch(
+            p1=np.array([0.0, 0.0]),
+            p2=np.array([1.0, 0.0]),
+            seg_starts=np.array([[0.0, 1.0]]),
+            seg_ends=np.array([[1.0, 1.0]]),
+        )
+        assert result[0] == False
+
+    def test_non_crossing(self):
+        """Segments that don't reach each other."""
+        result = line_segments_intersect_batch(
+            p1=np.array([0.0, 0.0]),
+            p2=np.array([0.5, 0.5]),
+            seg_starts=np.array([[0.8, 0.0]]),
+            seg_ends=np.array([[0.8, 1.0]]),
+        )
+        assert result[0] == False
+
+    def test_multiple_segments(self):
+        """Batch test with multiple segments."""
+        result = line_segments_intersect_batch(
+            p1=np.array([0.0, 0.0]),
+            p2=np.array([1.0, 1.0]),
+            seg_starts=np.array([
+                [0.0, 1.0],   # crosses
+                [2.0, 0.0],   # doesn't cross
+                [0.5, 0.0],   # crosses
+            ]),
+            seg_ends=np.array([
+                [1.0, 0.0],   # crosses
+                [2.0, 1.0],   # doesn't cross
+                [0.5, 1.0],   # crosses
+            ]),
+        )
+        assert result[0] == True
+        assert result[1] == False
+        assert result[2] == True
+
+
+if __name__ == "__main__":
+    instance = TestLineSegmentIntersect()
+    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.")