Fix lint debt and make CI gates honest

- ruff: fix all 328 errors (autofix + manual); move config to [tool.ruff.lint]
- mypy: fix all errors (annotations, nullable-column guards, stale kwargs
  in weekly report caller)
- black: reformat src/tests so black --check passes
- CI: remove `|| true` from ruff/black/mypy/pytest steps in both
  .gitea and .github workflows; install project deps and add mypy
  step in gitea python-ci so gates actually run
- docs: move 14 root status/guide markdown files into docs/, update links

tests/conftest.py

@@ -22,8 +22,8 @@ def test_db_session() -> Session:
     engine = create_engine("sqlite:///:memory:", echo=False)
     Base.metadata.create_all(engine)
 
-    TestSessionLocal = sessionmaker(bind=engine)
-    session = TestSessionLocal()
+    session_factory = sessionmaker(bind=engine)
+    session = session_factory()
 
     yield session