Stateless deployments / Quack Protocol Support

[explodingcamera]

• Support the quack remote protocol (https://duckdb.org/2026/05/12/quack-remote-protocol) to support non-persistent deployments
• Move user data from sqlite to a DuckDB database to reduce external dependencies / binary size
• (maybe) support using postgres as a remote duckdb catalog. This would probably have a fairly big performance impact from what I've seen in benchmarks, but pg_duckdb might help with that by running queries on the postgres server.