refactor: skip real DB connections entirely in REPLAY mode

[jy-tan]

Summary

Changes REPLAY mode behavior to use MockConnection directly without attempting real database connections. This enables true dependency-free replay where no database server is required at all.

Changes

• psycopg & psycopg2: In REPLAY mode, skip real DB connection attempts entirely and use MockConnection directly
  • Previously: Tried to connect to real DB, fell back to mock on failure
  • Now: Uses mock immediately without any connection attempt
  • Benefit: Faster startup, no DB server required, truly dependency-free replay
• psycopg2: Fix django_prometheus compatibility by setting a default cursor_factory when None is provided
  • django_prometheus does conn.cursor_factory or Cursor() which fails if cursor_factory is None

[cubic-dev-ai]

No issues found across 2 files