RocksDB and BoltDB support #524

Support embedded/local database engines like RocksDB and BoltDB.

These are key-value stores that run in-process (no server needed). Users want to browse and manage local database files directly from TablePro, similar to how SQLite works today.

Candidates:

• RocksDB - LSM-tree key-value store (Facebook). Widely used as storage backend (CockroachDB, TiKV, Kafka Streams).
• BoltDB - B+tree key-value store (pure Go, used by etcd). Read-optimized, single-file.

Both would open a local file and expose key-value pairs in the data grid.

Needs investigation:

• C/C++ client libraries available for static linking
• What "tables" and "columns" look like for a key-value store (column families for RocksDB, buckets for BoltDB)
• Read-only vs read-write support