Fix error handling in token-spy db_postgres.py

[bugman-007]

Summary

• Replace broad except Exception: with specific database exceptions per CLAUDE.md error handling rules
• Affects PostgreSQL database operations in token-spy service

Changes

• _get_or_create_agent(): Catch psycopg2.DatabaseError and psycopg2.OperationalError instead of Exception
• log_usage(): Catch psycopg2.DatabaseError and psycopg2.OperationalError instead of Exception

CLAUDE.md Compliance

Fixes violation of: "No broad or silent catches. Never except Exception: pass or except Exception: return None. No retry/backoff loops. No fallback chains."

These are database I/O boundaries where specific exception types map to distinct, meaningful statuses (connection errors, transaction errors, etc.).

[Lightheartdevs]

Closing as part of v2.1.0 stabilization. We're pausing new feature PRs while we solidify the installer and CI gates. If this is still relevant for v2.2.0 (targeting April 1), please rebase and resubmit. Thank you for contributing.