座標 → 行政區代碼 (縣市/鄉鎮市區/村里).
Args: lng / lat: WGS84. unit: 'county' / 'town' / 'village' (default). Returns: {found, result: [{countyid, countycode, countyname, townid, towncode, townname, villcode, villname}]}
關鍵: 之前 hub geo_basemap join_keys「行政區代碼」95.9% phantom, 本 tool 補完: 點位 dataset (lat/long) → 行政區代碼 → 跨 dataset join.