style: fix all ruff and eslint errors across codebase

Backend (ruff):
- Fix 106 errors: move imports to top of file (E402)
- Remove unused imports (F401)
- Add missing imports for undefined names (F821)
- Remove unused variables (F841)
- Fix test_models.py broken RefreshToken test
- Fix test_projects_api.py missing TestClient import

Frontend (eslint):
- Remove unused imports/variables across 10 files
- Fix explicit any types in client.ts and sessions.ts
- Clean up empty block statements in terminal.tsx

Quality gates: ruff (pass), eslint (pass), tsc --noEmit (pass),
pytest (98 passed, 4 pre-existing failures)

apps/api/src/auth/dependencies.py

@@ -7,6 +7,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from src.auth.session import decode_session_cookie
 from src.config import Settings
 from src.database import SessionLocal
+from src.models.project import Project
 from src.models.user import User