M2-T09: build data visualization UI (heatmap map as home page)

- self-contained RecordsMap (only module importing leaflet/react-leaflet/
  leaflet.heat/leaflet.markercluster); OSM tiles, swappable behind clean props
- heatmap layers for location + poo (primary); time-range selector fetches
  only the window (locations server-filtered; poo client-filtered)
- toggleable scatter layer with marker clustering; point-select reuses T10's
  edit/delete modals + hooks; query-key prefixes refresh map on mutation
- pure map logic isolated + unit-tested; leaflet mocked in component tests
- responsive layout; typed client only

frontend/package.json

@@ -16,9 +16,15 @@
     "@mantine/core": "^7.17.8",
     "@mantine/hooks": "^7.17.8",
     "@tanstack/react-query": "^5.101.0",
+    "@types/leaflet": "^1.9.21",
+    "@types/leaflet.markercluster": "^1.5.6",
+    "leaflet": "^1.9.4",
+    "leaflet.heat": "^0.2.0",
+    "leaflet.markercluster": "^1.5.3",
     "openapi-fetch": "^0.17.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "react-leaflet": "^4.2.1",
     "react-router-dom": "^6.30.4"
   },
   "devDependencies": {