fix(seed): use SQLAlchemy .is_not(None) instead of Python 'is not None' in queries

The reset_all_data() function used `ContentPage.store_id is not None` which
is a Python identity check (always True), causing it to delete ALL content
pages including platform defaults. Same bug in print_summary() caused the
count to always show 0 platform pages. Fixed both to use proper SQLAlchemy
.is_(None) / .is_not(None) syntax.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/seed/seed_demo.py

@@ -707,7 +707,7 @@ def reset_all_data(db: Session):
     for table in tables_to_clear:
         if table == ContentPage:
             # Only delete store content pages, keep platform defaults
-            db.execute(delete(ContentPage).where(ContentPage.store_id is not None))
+            db.execute(delete(ContentPage).where(ContentPage.store_id.is_not(None)))
         else:
             db.execute(delete(table))
 
@@ -1416,8 +1416,8 @@ def print_summary(db: Session):
     team_member_count = db.query(StoreUser).count()
     customer_count = db.query(Customer).count()
     product_count = db.query(Product).count()
-    platform_pages = db.query(ContentPage).filter(ContentPage.store_id is None).count()
-    store_pages = db.query(ContentPage).filter(ContentPage.store_id is not None).count()
+    platform_pages = db.query(ContentPage).filter(ContentPage.store_id.is_(None)).count()
+    store_pages = db.query(ContentPage).filter(ContentPage.store_id.is_not(None)).count()
 
     print("\n📊 Database Status:")
     print(f"  Merchants:        {merchant_count}")