mobilitydb-clustering-duckdb-bridge-dynlink

Phase A dynlink-mode duckdb bridge for mobilitydb_clustering (target mobilitydb_clustering).

The bridge imports only compose:dynlink/linker and dispatches SQL scalar arms as CBOR envelopes through the resident provider mobilitydb_clustering-composed. Aggregate / cast / table / pragma / column paths return duckerror::unsupported at Phase A scope.