fix: resolve lint errors in test files [CAR-932]

Fix 56 lint errors in test files that were blocking CI:
- E501: Split long SQL INSERT statements across multiple lines
- F401: Remove unused imports (os, unittest.mock.patch)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

tests/conftest.py

@@ -177,8 +177,10 @@ async def _create_test_user_and_session(
     async with db_engine.begin() as conn:
         await conn.execute(
             text(
-                "INSERT INTO users (id, email, hashed_password, display_name, email_verified, created_at, updated_at) "
-                "VALUES (:id, :email, :hashed_password, :display_name, :email_verified, :created_at, :updated_at)"
+                "INSERT INTO users (id, email, hashed_password, display_name, "
+                "email_verified, created_at, updated_at) "
+                "VALUES (:id, :email, :hashed_password, :display_name, :email_verified, "
+                ":created_at, :updated_at)"
             ),
             {
                 "id": user_id,