fix: resolve all ruff lint errors and type checker warnings

- Use Annotated[str, Form()] for FastAPI dependencies (FAST002)
- Add missing type annotations across src/ and tests/ (ANN001/003/201/202)
- Reduce function arguments via request.form() reads (PLR0913)
- Combine return paths to reduce return statements (PLR0911)
- Use anyio.Path for async-safe filesystem operations (ASYNC240)
- Extract constants, helpers, and dict comprehensions for clarity
- Move inline imports to top-level (PLC0415)
- Use raw strings for regex match patterns (RUF043)
- Fix redundant get_session_user call in delete_user (not-iterable)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_store/test_sqlite_user_repo.py

@@ -1,3 +1,5 @@
+from typing import Any
+
 import aiosqlite
 import pytest
 
@@ -12,7 +14,7 @@ def user_repo(db: aiosqlite.Connection) -> SQLiteUserRepository:
     return SQLiteUserRepository(db)
 
 
-def _make_user(**overrides) -> User:
+def _make_user(**overrides: Any) -> User:
     defaults = {"userid": "lusab-bansen", "username": "alice"}
     defaults.update(overrides)
     return User(**defaults)