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/core/definition.py

@@ -66,7 +66,6 @@ core_module = ModuleDefinition(
             "dashboard",
             "settings",
             "email-templates",
-            "my-menu",
         ],
         FrontendType.STORE: [
             "dashboard",
@@ -112,15 +111,6 @@ core_module = ModuleDefinition(
                         order=10,
                         is_mandatory=True,
                     ),
-                    MenuItemDefinition(
-                        id="my-menu",
-                        label_key="core.menu.my_menu",
-                        icon="view-grid",
-                        route="/admin/my-menu",
-                        order=30,
-                        is_mandatory=True,
-                        is_super_admin_only=True,
-                    ),
                 ],
             ),
         ],