## Summary
This PR upgrades backend typing tooling and finalizes quality cleanup for the SQLAlchemy async engine/session work on `PP-11_Add_SQLAlchemy_async_engine_session`.
## What Changed
- Upgraded pinned `pyright` version from `1.1.406` to `1.1.410`.
- Regenerated backend lock state to align with the new pyright pin.
- Removed deprecated `pythonPath` from pyright config to eliminate the config notice.
- Refined backend DB runtime state handling and cleanup paths.
- Updated database tests to avoid brittle singleton assumptions and keep typeguard-compatible async engine test doubles.
## Why
- Remove tooling noise and keep checks deterministic.
- Keep backend static/type/doc/test quality gates warning-free.
- Improve reliability and clarity of DB engine/session lifecycle tests.
## Validation
- `uv run ruff format --check .`
- `uv run ruff check .`
- `uv run pyright .`
- `uv run pydoclint --config=pyproject.toml src/`
- `uv run xdoctest --module backend`
- `uv run pytest`
Results:
- Pyright: `0 errors, 0 warnings`
- Pytest: `21 passed`
## Impact
- No API contract changes intended.
- No frontend changes.
- Backend behavior remains the same; this is tooling/test/runtime-state cleanup.
## Risk
- Low risk.
- Main touched areas are backend tooling config, lockfile, DB runtime state internals, and tests.
## Checklist
- [x] Backend lint clean
- [x] Backend type checks clean
- [x] Backend doc checks clean
- [x] Backend tests passing
- [x] Branch pushed and ready for review
Co-authored-by: copilotcoder <copilotcoder@darkhelm.org>
Reviewed-on: #67
