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/definition.py

@@ -188,6 +188,13 @@ tenancy_module = ModuleDefinition(
                         route="/merchants/account/stores",
                         order=10,
                     ),
+                    MenuItemDefinition(
+                        id="team",
+                        label_key="tenancy.menu.team",
+                        icon="user-group",
+                        route="/merchants/account/team",
+                        order=15,
+                    ),
                     MenuItemDefinition(
                         id="profile",
                         label_key="tenancy.menu.profile",
@@ -211,6 +218,7 @@ tenancy_module = ModuleDefinition(
                         icon="user-group",
                         route="/store/{store_code}/team",
                         order=5,
+                        requires_permission="team.view",
                     ),
                     MenuItemDefinition(
                         id="roles",