fix(billing): complete billing module — fix tier change, platform support, merchant portal

- Fix admin tier change: resolve tier_code→tier_id in update_subscription(),
  delegate to billing_service.change_tier() for Stripe-connected subs
- Add platform support to admin tiers page: platform column, filter dropdown,
  platform selector in create/edit modal, platform_name in tier API response
- Filter used platforms in create subscription modal on merchant detail page
- Enrich merchant portal API responses with tier code, tier_name, platform_name
- Add eager-load of platform relationship in get_merchant_subscription()
- Remove stale store_name/store_code references from merchant templates
- Add merchant tier change endpoint (POST /change-tier) and tier selector UI
  replacing broken requestUpgrade() button
- Fix subscription detail link to use platform_id instead of sub.id

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/tenancy/tests/unit/test_team_model.py

@@ -0,0 +1,138 @@
+# tests/unit/models/database/test_team.py
+"""Unit tests for StoreUser and Role database models."""
+
+import pytest
+
+from app.modules.tenancy.models import Role, Store, StoreUser
+
+
+@pytest.mark.unit
+@pytest.mark.database
+class TestRoleModel:
+    """Test Role model."""
+
+    def test_role_creation(self, db, test_store):
+        """Test Role model creation."""
+        role = Role(
+            store_id=test_store.id,
+            name="Manager",
+            permissions=["products.create", "orders.view"],
+        )
+        db.add(role)
+        db.commit()
+        db.refresh(role)
+
+        assert role.id is not None
+        assert role.store_id == test_store.id
+        assert role.name == "Manager"
+        assert "products.create" in role.permissions
+        assert "orders.view" in role.permissions
+
+    def test_role_default_permissions(self, db, test_store):
+        """Test Role model with default empty permissions."""
+        role = Role(
+            store_id=test_store.id,
+            name="Viewer",
+        )
+        db.add(role)
+        db.commit()
+        db.refresh(role)
+
+        assert role.permissions == [] or role.permissions is None
+
+    def test_role_store_relationship(self, db, test_store):
+        """Test Role-Store relationship."""
+        role = Role(
+            store_id=test_store.id,
+            name="Admin",
+            permissions=["*"],
+        )
+        db.add(role)
+        db.commit()
+        db.refresh(role)
+
+        assert role.store is not None
+        assert role.store.id == test_store.id
+
+
+@pytest.mark.unit
+@pytest.mark.database
+class TestStoreUserModel:
+    """Test StoreUser model."""
+
+    def test_store_user_creation(self, db, test_store, test_user):
+        """Test StoreUser model for team management."""
+        # Create a role
+        role = Role(
+            store_id=test_store.id,
+            name="Manager",
+            permissions=["products.create", "orders.view"],
+        )
+        db.add(role)
+        db.commit()
+
+        # Create store user
+        store_user = StoreUser(
+            store_id=test_store.id,
+            user_id=test_user.id,
+            role_id=role.id,
+            is_active=True,
+        )
+        db.add(store_user)
+        db.commit()
+        db.refresh(store_user)
+
+        assert store_user.id is not None
+        assert store_user.store_id == test_store.id
+        assert store_user.user_id == test_user.id
+        assert store_user.role.name == "Manager"
+        assert "products.create" in store_user.role.permissions
+
+    def test_store_user_relationships(self, db, test_store, test_user):
+        """Test StoreUser relationships."""
+        role = Role(
+            store_id=test_store.id,
+            name="Staff",
+            permissions=["orders.view"],
+        )
+        db.add(role)
+        db.commit()
+
+        store_user = StoreUser(
+            store_id=test_store.id,
+            user_id=test_user.id,
+            role_id=role.id,
+            is_active=True,
+        )
+        db.add(store_user)
+        db.commit()
+        db.refresh(store_user)
+
+        assert store_user.store is not None
+        assert store_user.user is not None
+        assert store_user.role is not None
+        assert store_user.store.store_code == test_store.store_code
+        assert store_user.user.email == test_user.email
+
+    def test_store_user_with_active_flag(self, db, test_store, test_user):
+        """Test StoreUser is_active field."""
+        role = Role(
+            store_id=test_store.id,
+            name="Default",
+            permissions=[],
+        )
+        db.add(role)
+        db.commit()
+
+        # Create with explicit is_active=True
+        store_user = StoreUser(
+            store_id=test_store.id,
+            user_id=test_user.id,
+            role_id=role.id,
+            is_active=True,
+        )
+        db.add(store_user)
+        db.commit()
+        db.refresh(store_user)
+
+        assert store_user.is_active is True