feat: multi-module improvements across merchant, store, i18n, and customer systems

- Fix platform-grouped merchant sidebar menu with core items at root level
- Add merchant store management (detail page, create store, team page)
- Fix store settings 500 error by removing dead stripe/API tab
- Move onboarding translations to module-owned locale files
- Fix onboarding banner i18n with server-side rendering + context inheritance
- Refactor login language selectors to use languageSelector() function (LANG-002)
- Move HTTPException handling to global exception handler in merchant routes (API-003)
- Add language selector to all login pages and portal headers
- Fix customer module: drop order stats from customer model, add to orders module
- Fix admin menu config visibility for super admin platform context
- Fix storefront auth and layout issues
- Add missing i18n translations for onboarding steps (en/fr/de/lb)

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

app/modules/orders/models/__init__.py

@@ -5,6 +5,7 @@ Orders module database models.
 This module contains the canonical implementations of order-related models.
 """
 
+from app.modules.orders.models.customer_order_stats import CustomerOrderStats
 from app.modules.orders.models.invoice import (
     Invoice,
     InvoiceStatus,
@@ -15,6 +16,7 @@ from app.modules.orders.models.order import Order, OrderItem
 from app.modules.orders.models.order_item_exception import OrderItemException
 
 __all__ = [
+    "CustomerOrderStats",
     "Order",
     "OrderItem",
     "OrderItemException",