feat: forward setup, server_settings, connection_class in pool/conn factories

[rcbevans]

Summary

make_pg_pool_factory and make_dedicated_conn_factory now accept three new keyword-only parameters and conditionally forward them to asyncpg.create_pool / asyncpg.connect:

• setup -- per-acquire hook that runs on every pool.acquire(), distinct from init which runs once per new physical connection. Use it for per-checkout work like resetting search_path or verifying session state.
• server_settings -- session-level GUCs applied at connection time (e.g. {"statement_timeout": "30s", "search_path": "app"}).
• connection_class -- custom asyncpg.Connection subclass for codec registration or method overrides.

Backward compatibility

All three params default to None and are omitted from the kwargs dict when not provided, following the same if not None pattern as the existing init and command_timeout params. Existing callers are byte-for-byte unaffected -- no new kwargs reach asyncpg when the params are absent.

Tests

• Each param is verified to reach asyncpg.create_pool / asyncpg.connect verbatim (identity check on the passed object).
• A backward-compat guard test confirms none of the new kwargs appear when the params are not provided.
• Also cleaned up emdashes and box-drawing section dividers in auth.py and test_auth.py (replaced with plain ASCII).

uv run ruff format .  # 475 files left unchanged
uv run ruff check .   # All checks passed
uv run pytest tests/test_auth.py  # all pass