fix(cms): storefront renders sections for landing pages + fix nav URLs

Two critical fixes for POC site rendering:

1. Storefront content page route now selects template based on
   page.template field: 'full' → landing-full.html (section-based),
   'modern'/'minimal' → their respective templates. Default stays
   content-page.html (plain HTML). Previously always used content-page
   which ignores page.sections JSON.

2. Storefront base_url uses store.subdomain (lowercase, hyphens)
   instead of store.store_code (uppercase, underscores) for URL
   building. Nav links now point to correct paths that the store
   context middleware can resolve.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/cms/routes/pages/storefront.py

@@ -109,8 +109,16 @@ async def generic_content_page(
     context = get_storefront_context(request, db=db, page=page)
     context["page_content"] = page_content
 
+    # Select template based on page.template field
+    template_map = {
+        "full": "cms/storefront/landing-full.html",
+        "modern": "cms/storefront/landing-modern.html",
+        "minimal": "cms/storefront/landing-minimal.html",
+    }
+    template_name = template_map.get(page.template, "cms/storefront/content-page.html")
+
     return templates.TemplateResponse(
-        "cms/storefront/content-page.html",
+        template_name,
         context,
     )