feat: add PostgreSQL performance logging to PostgresCRUDRepository

[smoreinis]

Summary

• Add optional performance logging for all PostgreSQL CRUD operations in PostgresCRUDRepository
• Track query execution time, detect slow queries, and emit StatsD metrics
• Support both global configuration via environment variables and per-query opt-in

Changes

• New utility: src/utils/postgres_perf_logging.py - Performance logging with QueryType enum, QueryMetrics dataclass, and PostgresPerformanceLogger class
• Environment variables: Added 3 new config options:
  • POSTGRES_PERF_LOGGING_ENABLED (default: false)
  • POSTGRES_SLOW_QUERY_THRESHOLD_MS (default: 100ms)
  • POSTGRES_PERF_LOGGING_SAMPLE_RATE (default: 1.0)
• CRUD methods: Added optional perf_logging parameter to all methods (create, get, list, update, delete, etc.)
• StatsD metrics: postgres.query.duration (histogram), postgres.query.count, postgres.query.slow (counters)
• Unit tests: 17 new tests covering all functionality

Usage

Enable globally:

POSTGRES_PERF_LOGGING_ENABLED=true
POSTGRES_SLOW_QUERY_THRESHOLD_MS=50

Per-query override:

# Force enable
agent = await agent_repo.get(id="123", perf_logging=True)

# Force disable for high-frequency queries
result = await repo.list(filters={...}, perf_logging=False)

Test plan

• All 17 new unit tests pass
• All 196 existing unit tests pass
• Manual testing with POSTGRES_PERF_LOGGING_ENABLED=true