Fix all 33 ruff linting errors causing CI failures

- Remove unused imports (F401) across 17 files
- Fix f-strings without placeholders (F541) in 3 files
- Add noqa: E712 to SQLAlchemy == True comparisons (valid ORM pattern)
- Preserve alembic side-effect import with noqa: F401

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
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backend/tests/conftest.py

@@ -3,8 +3,7 @@ Test configuration and fixtures.
 """
 
 import pytest
-import asyncio
-from typing import AsyncGenerator, Generator
+from typing import AsyncGenerator
 from httpx import AsyncClient
 from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
 from sqlalchemy.pool import NullPool