feat(cms): CMS-driven homepages, products section, placeholder resolution

- Add ProductCard/ProductsSection schema and _products.html section macro
- Rewrite seed script with 3-platform homepage sections (wizard, OMS, loyalty),
  platform marketing pages, and store defaults with {{store_name}} placeholders
- Add resolve_placeholders() to ContentPageService for store default pages
- Fix SQLAlchemy filter bugs: replace Python `is None` with `.is_(None)` across
  all ContentPageService query methods (was silently breaking all platform page lookups)
- Remove hardcoded orion fallback and delete homepage-orion.html
- Add placeholder hint box with click-to-copy in admin content page editor
- Export ProductCard/ProductsSection from cms schemas __init__

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

app/modules/cms/schemas/__init__.py

@@ -31,6 +31,8 @@ from app.modules.cms.schemas.homepage_sections import (
     HomepageSections,
     HomepageSectionsResponse,
     PricingSection,
+    ProductCard,
+    ProductsSection,
     # API schemas
     SectionUpdateRequest,
     # Translatable text
@@ -92,6 +94,8 @@ __all__ = [
     "HeroSection",
     "FeatureCard",
     "FeaturesSection",
+    "ProductCard",
+    "ProductsSection",
     "PricingSection",
     "CTASection",
     "HomepageSections",