Add parts label migration script

migrate_add_part_labels.py

@@ -0,0 +1,56 @@
+"""
+Migration: parts drawer labelling.
+
+Creates part_categories and part_labels, makes uploads/parts, and seeds the
+starter taxonomy. Safe to run more than once - every step checks first.
+
+    python migrate_add_part_labels.py
+
+You do not strictly need this: app/services/schema_upgrade.py creates both
+tables at boot once the wiring patch is applied. It exists so you can run the
+change deliberately, and see what it did, before restarting the service.
+
+Created by: Jess Rogerson (yelling commands at Claude.AI)
+"""
+
+import os
+import sys
+
+from sqlalchemy import inspect
+
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+
+from app import create_app, db  # noqa: E402
+from app.models.part_label import PartCategory, PartLabel  # noqa: E402
+from app.services.part_catalog import seed_categories  # noqa: E402
+
+
+def main():
+    app = create_app(os.environ.get('FLASK_CONFIG', 'default'))
+
+    with app.app_context():
+        inspector = inspect(db.engine)
+        existing = set(inspector.get_table_names())
+
+        for model in (PartCategory, PartLabel):
+            if model.__tablename__ in existing:
+                print(f'  = table {model.__tablename__} already present')
+            else:
+                model.__table__.create(db.engine, checkfirst=True)
+                print(f'  + created table {model.__tablename__}')
+
+        parts_folder = os.path.join(app.config['UPLOAD_FOLDER'], 'parts')
+        os.makedirs(parts_folder, exist_ok=True)
+        print(f'  = part images folder: {parts_folder}')
+
+        created = seed_categories(force=True)
+        if created:
+            print(f'  + seeded {created} categories')
+        else:
+            print('  = categories already seeded (nothing changed)')
+
+        print('\nDone. Parts Labels lives at /admin/labels (admins only).')
+
+
+if __name__ == '__main__':
+    main()