Fix ruff lint errors across codebase

- Auto-fix F401 (unused imports) and I001 (unsorted imports) with ruff --fix
- Manually fix E501 (line too long) in alembic migrations and src/ models
- Run ruff format to ensure consistent formatting

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

alembic/versions/004_fix_user_id_text.py

@@ -40,7 +40,12 @@ def upgrade() -> None:
             return  # already TEXT — nothing to do
 
     # Step 1: Drop existing FK constraints (ignore if they don't exist)
-    op.execute(text("ALTER TABLE user_store_accounts DROP CONSTRAINT IF EXISTS user_store_accounts_user_id_fkey"))
+    op.execute(
+        text(
+            "ALTER TABLE user_store_accounts "
+            "DROP CONSTRAINT IF EXISTS user_store_accounts_user_id_fkey"
+        )
+    )
     op.execute(text("ALTER TABLE purchases DROP CONSTRAINT IF EXISTS purchases_user_id_fkey"))
 
     # Step 2: Alter users.id from uuid to text
@@ -89,7 +94,12 @@ def upgrade() -> None:
 
 def downgrade() -> None:
     # Drop FK constraints
-    op.execute(text("ALTER TABLE user_store_accounts DROP CONSTRAINT IF EXISTS user_store_accounts_user_id_fkey"))
+    op.execute(
+        text(
+            "ALTER TABLE user_store_accounts "
+            "DROP CONSTRAINT IF EXISTS user_store_accounts_user_id_fkey"
+        )
+    )
     op.execute(text("ALTER TABLE purchases DROP CONSTRAINT IF EXISTS purchases_user_id_fkey"))
 
     # Revert users.id from text to uuid