feat: implement /platforms/ URL prefix routing strategy

- Update middleware to use /platforms/{code}/ prefix for dev routing
- Change DEFAULT_PLATFORM_CODE from 'oms' to 'main'
- Add 'main' platform for main marketing site (wizamart.lu)
- Remove hardcoded /oms and /loyalty routes from main.py
- Update platform_pages.py homepage to handle vendor landing pages

URL structure:
- localhost:9999/ → Main marketing site ('main' platform)
- localhost:9999/platforms/oms/ → OMS platform
- localhost:9999/platforms/loyalty/ → Loyalty platform
- oms.lu/ → OMS platform (production)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/routes/platform_pages.py

@@ -90,16 +90,102 @@ async def homepage(
     db: Session = Depends(get_db),
 ):
     """
-    Platform marketing homepage.
+    Homepage handler.
 
-    Displays:
-    - Hero section with value proposition
-    - Pricing tier cards
-    - Add-ons section
-    - Letzshop vendor finder
-    - Call to action for signup
+    Handles two scenarios:
+    1. Vendor on custom domain (vendor.com) → Show vendor landing page or redirect to shop
+    2. Platform marketing site → Show platform homepage from CMS or default template
+
+    URL routing:
+    - localhost:9999/             → Main marketing site ('main' platform)
+    - localhost:9999/platforms/oms/ → OMS platform (middleware rewrites to /)
+    - oms.lu/                     → OMS platform (domain-based)
+    - shop.mycompany.com/         → Vendor landing page (custom domain)
     """
+    from fastapi.responses import RedirectResponse
+
+    # Get platform and vendor from middleware
+    platform = getattr(request.state, "platform", None)
+    vendor = getattr(request.state, "vendor", None)
+
+    # Scenario 1: Vendor detected (custom domain like vendor.com)
+    if vendor:
+        logger.debug(f"[HOMEPAGE] Vendor detected: {vendor.subdomain}")
+
+        # Get platform_id (use platform from context or default to 1 for OMS)
+        platform_id = platform.id if platform else 1
+
+        # Try to find vendor landing page (slug='landing' or 'home')
+        landing_page = content_page_service.get_page_for_vendor(
+            db, platform_id=platform_id, slug="landing", vendor_id=vendor.id, include_unpublished=False
+        )
+
+        if not landing_page:
+            landing_page = content_page_service.get_page_for_vendor(
+                db, platform_id=platform_id, slug="home", vendor_id=vendor.id, include_unpublished=False
+            )
+
+        if landing_page:
+            # Render landing page with selected template
+            from app.routes.shop_pages import get_shop_context
+
+            template_name = landing_page.template or "default"
+            template_path = f"vendor/landing-{template_name}.html"
+
+            logger.info(f"[HOMEPAGE] Rendering vendor landing page: {template_path}")
+            return templates.TemplateResponse(
+                template_path, get_shop_context(request, db=db, page=landing_page)
+            )
+
+        # No landing page - redirect to shop
+        vendor_context = getattr(request.state, "vendor_context", None)
+        access_method = (
+            vendor_context.get("detection_method", "unknown")
+            if vendor_context
+            else "unknown"
+        )
+
+        if access_method == "path":
+            full_prefix = (
+                vendor_context.get("full_prefix", "/vendor/")
+                if vendor_context
+                else "/vendor/"
+            )
+            return RedirectResponse(
+                url=f"{full_prefix}{vendor.subdomain}/shop/", status_code=302
+            )
+        # Domain/subdomain - redirect to /shop/
+        return RedirectResponse(url="/shop/", status_code=302)
+
+    # Scenario 2: Platform marketing site (no vendor)
+    # Try to load platform homepage from CMS
+    platform_id = platform.id if platform else 1
+
+    cms_homepage = content_page_service.get_platform_page(
+        db, platform_id=platform_id, slug="home", include_unpublished=False
+    )
+
+    if not cms_homepage:
+        cms_homepage = content_page_service.get_platform_page(
+            db, platform_id=platform_id, slug="platform_homepage", include_unpublished=False
+        )
+
+    if cms_homepage:
+        # Use CMS-based homepage with template selection
+        context = get_platform_context(request, db)
+        context["page"] = cms_homepage
+        context["platform"] = platform
+
+        template_name = cms_homepage.template or "default"
+        template_path = f"platform/homepage-{template_name}.html"
+
+        logger.info(f"[HOMEPAGE] Rendering CMS homepage with template: {template_path}")
+        return templates.TemplateResponse(template_path, context)
+
+    # Fallback: Default wizamart homepage (no CMS content)
+    logger.info("[HOMEPAGE] No CMS homepage found, using default wizamart template")
     context = get_platform_context(request, db)
+    context["platform"] = platform
 
     # Fetch tiers for display (use API service internally)
     from models.database.subscription import TIER_LIMITS, TierCode