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/tests/integration/test_merchant_menu_routes.py

@@ -263,34 +263,49 @@ class TestMerchantMenuModuleGating:
 
     def test_loyalty_appears_when_module_enabled(
         self, client, db, menu_auth, menu_merchant, menu_subscription,
-        menu_loyalty_module,
+        menu_loyalty_module, menu_platform,
     ):
-        """Loyalty section appears when loyalty module is enabled on subscribed platform."""
+        """Loyalty items appear under platform section when module is enabled."""
         response = client.get(BASE, headers=menu_auth)
         assert response.status_code == 200
         data = response.json()
+        # Loyalty now appears under a platform-{code} section
+        platform_section_id = f"platform-{menu_platform.code}"
         section_ids = {s["id"] for s in data["sections"]}
-        assert "loyalty" in section_ids
+        assert platform_section_id in section_ids
+        # Check loyalty item exists in that platform section
+        platform_section = next(
+            s for s in data["sections"] if s["id"] == platform_section_id
+        )
+        item_ids = {i["id"] for i in platform_section["items"]}
+        assert "loyalty-overview" in item_ids
 
     def test_loyalty_hidden_when_module_not_enabled(
         self, client, db, menu_auth, menu_merchant, menu_subscription,
+        menu_platform,
     ):
-        """Loyalty section is hidden when loyalty module is NOT enabled."""
+        """No platform section when no non-core modules are enabled."""
         response = client.get(BASE, headers=menu_auth)
         assert response.status_code == 200
         data = response.json()
+        platform_section_id = f"platform-{menu_platform.code}"
         section_ids = {s["id"] for s in data["sections"]}
-        assert "loyalty" not in section_ids
+        assert platform_section_id not in section_ids
 
     def test_loyalty_item_has_correct_route(
         self, client, db, menu_auth, menu_merchant, menu_subscription,
-        menu_loyalty_module,
+        menu_loyalty_module, menu_platform,
     ):
         """Loyalty overview item has the correct URL."""
         response = client.get(BASE, headers=menu_auth)
         data = response.json()
-        loyalty = next(s for s in data["sections"] if s["id"] == "loyalty")
-        overview = next(i for i in loyalty["items"] if i["id"] == "loyalty-overview")
+        platform_section_id = f"platform-{menu_platform.code}"
+        platform_section = next(
+            s for s in data["sections"] if s["id"] == platform_section_id
+        )
+        overview = next(
+            i for i in platform_section["items"] if i["id"] == "loyalty-overview"
+        )
         assert overview["url"] == "/merchants/loyalty/overview"
 
 
@@ -352,7 +367,8 @@ class TestMerchantMenuSubscriptionStatus:
         response = client.get(BASE, headers=menu_auth)
         assert response.status_code == 200
         section_ids = {s["id"] for s in response.json()["sections"]}
-        assert "loyalty" in section_ids
+        platform_section_id = f"platform-{menu_platform.code}"
+        assert platform_section_id in section_ids
 
     def test_expired_subscription_hides_non_core_modules(
         self, client, db, menu_auth, menu_merchant, menu_platform, menu_tier,
@@ -374,8 +390,9 @@ class TestMerchantMenuSubscriptionStatus:
         response = client.get(BASE, headers=menu_auth)
         assert response.status_code == 200
         section_ids = {s["id"] for s in response.json()["sections"]}
-        # Loyalty should NOT appear because subscription is expired
-        assert "loyalty" not in section_ids
+        platform_section_id = f"platform-{menu_platform.code}"
+        # Platform section should NOT appear because subscription is expired
+        assert platform_section_id not in section_ids
         # Core sections always appear
         assert "main" in section_ids
         assert "billing" in section_ids
@@ -468,9 +485,20 @@ class TestMerchantMenuMultiPlatform:
 
         response = client.get(BASE, headers=menu_auth)
         assert response.status_code == 200
-        section_ids = {s["id"] for s in response.json()["sections"]}
-        # Loyalty enabled on Platform A should appear in the union
-        assert "loyalty" in section_ids
+        data = response.json()
+        section_ids = {s["id"] for s in data["sections"]}
+        # Loyalty enabled on Platform A appears under platform-a's section
+        platform_a_section_id = f"platform-{platform_a.code}"
+        assert platform_a_section_id in section_ids
+        # Platform B has no non-core modules, so no section
+        platform_b_section_id = f"platform-{platform_b.code}"
+        assert platform_b_section_id not in section_ids
+        # Check loyalty item exists in Platform A section
+        pa_section = next(
+            s for s in data["sections"] if s["id"] == platform_a_section_id
+        )
+        item_ids = {i["id"] for i in pa_section["items"]}
+        assert "loyalty-overview" in item_ids
         # Core sections always present
         assert "main" in section_ids
         assert "billing" in section_ids

app/modules/core/tests/unit/test_menu_service.py

@@ -110,3 +110,62 @@ class TestMenuServiceMerchantRendering:
         without_ids = {s.id for s in without_loyalty}
         assert "loyalty" in with_ids
         assert "loyalty" not in without_ids
+
+
+@pytest.mark.unit
+@pytest.mark.core
+class TestMenuServiceMerchantByPlatform:
+    """Test get_merchant_menu_by_platform grouping logic."""
+
+    def setup_method(self):
+        self.service = MenuService()
+
+    def test_core_sections_contain_only_core_items(self, db):
+        """Core sections should only have items from core modules."""
+        from app.modules.core.services.menu_discovery_service import (
+            menu_discovery_service,
+        )
+        from app.modules.registry import MODULES
+
+        core_codes = {code for code, mod in MODULES.items() if mod.is_core}
+
+        core_sections = menu_discovery_service.get_menu_sections_for_frontend(
+            db,
+            FrontendType.MERCHANT,
+            enabled_module_codes=core_codes,
+        )
+        for section in core_sections:
+            section.items = [i for i in section.items if i.module_code in core_codes]
+
+        for section in core_sections:
+            for item in section.items:
+                assert item.module_code in core_codes, (
+                    f"Non-core item '{item.id}' (module={item.module_code}) "
+                    f"found in core section '{section.id}'"
+                )
+
+    def test_non_core_sections_for_loyalty(self, db):
+        """Non-core modules like loyalty produce merchant menu sections."""
+        from app.modules.core.services.menu_discovery_service import (
+            menu_discovery_service,
+        )
+        from app.modules.registry import MODULES
+
+        core_codes = {code for code, mod in MODULES.items() if mod.is_core}
+        non_core = {"loyalty"}
+
+        sections = menu_discovery_service.get_menu_sections_for_frontend(
+            db,
+            FrontendType.MERCHANT,
+            enabled_module_codes=non_core,
+        )
+        sections = [
+            s
+            for s in sections
+            if any(i.module_code in non_core for i in s.items)
+        ]
+
+        assert len(sections) > 0, "Loyalty module should produce merchant menu sections"
+        for section in sections:
+            for item in section.items:
+                assert item.module_code not in core_codes