feat: loyalty feature provider, admin data fixes, storefront mobile menu

- Add LoyaltyFeatureProvider with 11 BINARY/MERCHANT features for billing
  feature gating, wired into loyalty module definition
- Fix subscription-tiers admin page showing 0 features by populating
  feature_codes from tier relationship in all admin tier endpoints
- Fix merchants admin page showing 0 stores and N/A owner by adding
  store_count and owner_email to MerchantResponse and eager-loading owner
- Add "no tiers" warning with link in subscription creation modal when
  platform has no configured tiers
- Add missing mobile menu panel to storefront base template so hamburger
  toggle actually shows navigation links

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

tests/unit/modules/loyalty/test_loyalty_features.py

@@ -0,0 +1,92 @@
+# tests/unit/modules/loyalty/test_loyalty_features.py
+"""
+Unit tests for the loyalty feature provider.
+
+Tests cover:
+- Feature category
+- Feature declarations (count, codes, types, scopes)
+- Usage methods return empty lists
+- Protocol compliance
+"""
+
+import pytest
+
+from app.modules.contracts.features import (
+    FeatureProviderProtocol,
+    FeatureScope,
+    FeatureType,
+)
+from app.modules.loyalty.definition import loyalty_module
+from app.modules.loyalty.services.loyalty_features import (
+    LoyaltyFeatureProvider,
+    loyalty_feature_provider,
+)
+
+
+@pytest.mark.unit
+class TestLoyaltyFeatureProvider:
+    """Tests for LoyaltyFeatureProvider."""
+
+    def test_feature_category(self):
+        """Feature category should be 'loyalty'."""
+        assert loyalty_feature_provider.feature_category == "loyalty"
+
+    def test_get_feature_declarations_count(self):
+        """Should return exactly 11 feature declarations."""
+        declarations = loyalty_feature_provider.get_feature_declarations()
+        assert len(declarations) == 11
+
+    def test_feature_codes_match_module_definition(self):
+        """All declared feature codes should match loyalty_module.features."""
+        declarations = loyalty_feature_provider.get_feature_declarations()
+        declared_codes = {d.code for d in declarations}
+        module_features = set(loyalty_module.features)
+        assert declared_codes == module_features
+
+    def test_all_features_are_binary(self):
+        """All loyalty features should be BINARY type."""
+        declarations = loyalty_feature_provider.get_feature_declarations()
+        for decl in declarations:
+            assert decl.feature_type == FeatureType.BINARY, (
+                f"Feature {decl.code} should be BINARY, got {decl.feature_type}"
+            )
+
+    def test_all_features_are_merchant_scoped(self):
+        """All loyalty features should be MERCHANT scoped."""
+        declarations = loyalty_feature_provider.get_feature_declarations()
+        for decl in declarations:
+            assert decl.scope == FeatureScope.MERCHANT, (
+                f"Feature {decl.code} should be MERCHANT scoped, got {decl.scope}"
+            )
+
+    def test_all_features_have_name_key(self):
+        """All features should have a non-empty name_key."""
+        declarations = loyalty_feature_provider.get_feature_declarations()
+        for decl in declarations:
+            assert decl.name_key, f"Feature {decl.code} missing name_key"
+
+    def test_all_features_have_description_key(self):
+        """All features should have a non-empty description_key."""
+        declarations = loyalty_feature_provider.get_feature_declarations()
+        for decl in declarations:
+            assert decl.description_key, f"Feature {decl.code} missing description_key"
+
+    def test_get_store_usage_returns_empty(self):
+        """get_store_usage should return an empty list."""
+        result = loyalty_feature_provider.get_store_usage(db=None, store_id=1)
+        assert result == []
+
+    def test_get_merchant_usage_returns_empty(self):
+        """get_merchant_usage should return an empty list."""
+        result = loyalty_feature_provider.get_merchant_usage(
+            db=None, merchant_id=1, platform_id=1
+        )
+        assert result == []
+
+    def test_satisfies_feature_provider_protocol(self):
+        """Provider should satisfy FeatureProviderProtocol."""
+        assert isinstance(loyalty_feature_provider, FeatureProviderProtocol)
+
+    def test_singleton_is_correct_type(self):
+        """Singleton instance should be a LoyaltyFeatureProvider."""
+        assert isinstance(loyalty_feature_provider, LoyaltyFeatureProvider)