@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/geometry/haversine.py

@@ -0,0 +1,50 @@
+"""
+Distance calculations using the haversine formula.
+
+Supports both scalar and batch (NumPy array) operations.
+"""
+
+import numpy as np
+from typing import Tuple
+
+EARTH_RADIUS = 6371000  # meters
+
+
+def haversine_distance(lat1: float, lon1: float, lat2: float, lon2: float) -> float:
+    """Calculate distance between two points in meters."""
+    lat1, lon1, lat2, lon2 = map(np.radians, [lat1, lon1, lat2, lon2])
+    dlat = lat2 - lat1
+    dlon = lon2 - lon1
+    a = np.sin(dlat / 2) ** 2 + np.cos(lat1) * np.cos(lat2) * np.sin(dlon / 2) ** 2
+    c = 2 * np.arcsin(np.sqrt(a))
+    return float(EARTH_RADIUS * c)
+
+
+def haversine_batch(
+    lat1: float, lon1: float,
+    lats2: np.ndarray, lons2: np.ndarray,
+) -> np.ndarray:
+    """Distance from one point to many points (meters)."""
+    lat1_rad = np.radians(lat1)
+    lon1_rad = np.radians(lon1)
+    lats2_rad = np.radians(lats2)
+    lons2_rad = np.radians(lons2)
+
+    dlat = lats2_rad - lat1_rad
+    dlon = lons2_rad - lon1_rad
+
+    a = np.sin(dlat / 2) ** 2 + np.cos(lat1_rad) * np.cos(lats2_rad) * np.sin(dlon / 2) ** 2
+    c = 2 * np.arcsin(np.sqrt(a))
+
+    return EARTH_RADIUS * c
+
+
+def points_to_local_coords(
+    ref_lat: float, ref_lon: float,
+    lats: np.ndarray, lons: np.ndarray,
+) -> Tuple[np.ndarray, np.ndarray]:
+    """Convert lat/lon to local X/Y meters (equirectangular projection)."""
+    cos_lat = np.cos(np.radians(ref_lat))
+    x = (lons - ref_lon) * 111320.0 * cos_lat
+    y = (lats - ref_lat) * 110540.0
+    return x, y