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/tenancy/schemas/__init__.py

@@ -80,6 +80,9 @@ from app.modules.tenancy.schemas.merchant import (
     MerchantPortalProfileUpdate,
     MerchantPortalStoreListResponse,
     MerchantResponse,
+    MerchantStoreCreate,
+    MerchantStoreDetailResponse,
+    MerchantStoreUpdate,
     MerchantSummary,
     MerchantTransferOwnership,
     MerchantTransferOwnershipResponse,
@@ -163,6 +166,9 @@ __all__ = [
     "MerchantPortalProfileUpdate",
     "MerchantPortalStoreListResponse",
     "MerchantResponse",
+    "MerchantStoreCreate",
+    "MerchantStoreDetailResponse",
+    "MerchantStoreUpdate",
     "MerchantSummary",
     "MerchantTransferOwnership",
     "MerchantTransferOwnershipResponse",