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/customers/schemas/context.py

@@ -7,7 +7,6 @@ avoiding direct database model imports in the API layer.
 """
 
 from datetime import datetime
-from decimal import Decimal
 
 from pydantic import BaseModel, ConfigDict
 
@@ -45,11 +44,6 @@ class CustomerContext(BaseModel):
     marketing_consent: bool = False
     preferred_language: str | None = None
 
-    # Stats (for order placement)
-    total_orders: int = 0
-    total_spent: Decimal = Decimal("0.00")
-    last_order_date: datetime | None = None
-
     # Status
     is_active: bool = True
 
@@ -89,9 +83,6 @@ class CustomerContext(BaseModel):
             phone=customer.phone,
             marketing_consent=customer.marketing_consent,
             preferred_language=customer.preferred_language,
-            total_orders=customer.total_orders or 0,
-            total_spent=customer.total_spent or Decimal("0.00"),
-            last_order_date=customer.last_order_date,
             is_active=customer.is_active,
             created_at=customer.created_at,
             updated_at=customer.updated_at,