fix: add statement_timeout and lock_timeout to mirror_primary_tables to prevent FDW zombie locks

Add SET LOCAL timeouts to refresh_tables() to prevent FDW zombie
connections from holding ACCESS EXCLUSIVE locks on mirrored tables
indefinitely. This fixes a v0.42.0 regression where stuck FDW queries
during mirror_primary_tables() cascade into full system lock.

- statement_timeout=60s: kills stuck FDW queries (normally <5s)
- lock_timeout=10s: prevents TRUNCATE stampede from multiple nodes

Both are SET LOCAL (transaction-scoped), zero impact on other queries.