Function geonames_db_path 

pub fn geonames_db_path() -> PathBuf

Resolve GeoNames DB path.

Searches the same candidate roots as the rest of bootstrap (asset install dir, $SMRITI_ASSET_DIR / legacy $PHOTOVAULT_ASSET_DIR, executable dir, project root, /usr/lib/smriti, /usr/lib/photovault) plus the CWD-relative data/.