fix: judge camera catalog trimming by region, not by returned cameras

Coverage was checked only for packs among the cameras found, so an area
whose cameras were all trimmed away answered zero cameras, complete. The
catalog now reports where each trimmed pack's cameras are, and the tool
marks an answer partial whenever its area overlaps that region.

server/providers/cctv/normalize.js

@@ -471,11 +471,32 @@ export function prioritizeSources(cameras, maxCount, anchors) {
   });
 
   const kept = scored.slice(0, cap).map((entry) => entry.camera);
-  // How many cameras the pack offered before trimming, for coverage reports.
+  // How many cameras the pack offered before trimming, and where, for
+  // coverage reports.
   Object.defineProperty(kept, 'available', { value: list.length });
+  Object.defineProperty(kept, 'region', { value: cameraRegion(list) });
   return kept;
 }
 
+/** The bounding box of cameras with coordinates, or null. */
+export function cameraRegion(cameras) {
+  let region = null;
+  for (const camera of cameras || []) {
+    const lat = Number(camera?.lat);
+    const lon = Number(camera?.lon);
+    if (!Number.isFinite(lat) || !Number.isFinite(lon)) continue;
+    region = region
+      ? {
+          west: Math.min(region.west, lon),
+          south: Math.min(region.south, lat),
+          east: Math.max(region.east, lon),
+          north: Math.max(region.north, lat),
+        }
+      : { west: lon, south: lat, east: lon, north: lat };
+  }
+  return region;
+}
+
 /**
  * Normalize a raw CCTV source item into a canonical shape with safe defaults.
  *