feat(golemcore/supabase): add Supabase rows plugin

[golemcore1]

Summary

• add a new first-party golemcore/supabase plugin module and wire it into the Maven reactor and repository overview
• implement the supabase_rows tool with select_rows, insert_row, update_rows, and delete_rows operations backed by Supabase PostgREST plus plugin settings for project URL, API key, schema, defaults, and write/delete gates
• add registry metadata and focused tests for config normalization, tool parsing, rows service behavior, API client request mapping, dashboard settings actions, and Spring wiring