feat(billing): migrate frontend templates to feature provider system

Replace hardcoded subscription fields (orders_limit, products_limit,
team_members_limit) across 5 frontend pages with dynamic feature
provider APIs. Add admin convenience endpoint for store subscription
lookup. Remove legacy stubs (StoreSubscription, FeatureCode, Feature,
TIER_LIMITS, FeatureInfo, FeatureUpgradeInfo) and schema aliases.

Pages updated:
- Admin subscriptions: dynamic feature overrides editor
- Admin tiers: correct feature catalog/limits API URLs
- Store billing: usage metrics from /store/billing/usage
- Merchant subscription detail: tier.feature_limits rendering
- Admin store detail: new GET /admin/subscriptions/store/{id} endpoint

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

app/modules/billing/schemas/__init__.py

@@ -6,48 +6,47 @@ This is the canonical location for billing schemas.
 
 Usage:
     from app.modules.billing.schemas import (
-        SubscriptionCreate,
-        SubscriptionResponse,
+        MerchantSubscriptionCreate,
+        MerchantSubscriptionResponse,
         TierInfo,
     )
 """
 
 from app.modules.billing.schemas.subscription import (
     # Tier schemas
-    TierFeatures,
-    TierLimits,
+    TierFeatureLimitResponse,
     TierInfo,
-    # Subscription CRUD schemas
-    SubscriptionCreate,
-    SubscriptionUpdate,
-    SubscriptionResponse,
-    # Usage schemas
-    SubscriptionUsage,
-    UsageSummary,
-    SubscriptionStatusResponse,
+    # Subscription schemas
+    MerchantSubscriptionCreate,
+    MerchantSubscriptionUpdate,
+    MerchantSubscriptionResponse,
+    MerchantSubscriptionStatusResponse,
+    # Feature summary schemas
+    FeatureSummaryResponse,
     # Limit check schemas
     LimitCheckResult,
-    CanCreateOrderResponse,
-    CanAddProductResponse,
-    CanAddTeamMemberResponse,
     FeatureCheckResponse,
 )
 from app.modules.billing.schemas.billing import (
     # Subscription Tier Admin schemas
+    TierFeatureLimitEntry,
     SubscriptionTierBase,
     SubscriptionTierCreate,
     SubscriptionTierUpdate,
     SubscriptionTierResponse,
     SubscriptionTierListResponse,
-    # Vendor Subscription schemas
-    VendorSubscriptionResponse,
-    VendorSubscriptionWithVendor,
-    VendorSubscriptionListResponse,
-    VendorSubscriptionCreate,
-    VendorSubscriptionUpdate,
+    # Merchant Subscription Admin schemas
+    MerchantSubscriptionAdminResponse,
+    MerchantSubscriptionWithMerchant,
+    MerchantSubscriptionListResponse,
+    MerchantSubscriptionAdminCreate,
+    MerchantSubscriptionAdminUpdate,
+    # Merchant Feature Override schemas
+    MerchantFeatureOverrideEntry,
+    MerchantFeatureOverrideResponse,
     # Billing History schemas
     BillingHistoryResponse,
-    BillingHistoryWithVendor,
+    BillingHistoryWithMerchant,
     BillingHistoryListResponse,
     # Checkout & Portal schemas
     CheckoutRequest,
@@ -55,42 +54,44 @@ from app.modules.billing.schemas.billing import (
     PortalSessionResponse,
     # Stats schemas
     SubscriptionStatsResponse,
+    # Feature Catalog schemas
+    FeatureDeclarationResponse,
+    FeatureCatalogResponse,
 )
 
 __all__ = [
     # Tier schemas (subscription.py)
-    "TierFeatures",
-    "TierLimits",
+    "TierFeatureLimitResponse",
     "TierInfo",
-    # Subscription CRUD schemas (subscription.py)
-    "SubscriptionCreate",
-    "SubscriptionUpdate",
-    "SubscriptionResponse",
-    # Usage schemas (subscription.py)
-    "SubscriptionUsage",
-    "UsageSummary",
-    "SubscriptionStatusResponse",
+    # Subscription schemas (subscription.py)
+    "MerchantSubscriptionCreate",
+    "MerchantSubscriptionUpdate",
+    "MerchantSubscriptionResponse",
+    "MerchantSubscriptionStatusResponse",
+    # Feature summary schemas (subscription.py)
+    "FeatureSummaryResponse",
     # Limit check schemas (subscription.py)
     "LimitCheckResult",
-    "CanCreateOrderResponse",
-    "CanAddProductResponse",
-    "CanAddTeamMemberResponse",
     "FeatureCheckResponse",
     # Subscription Tier Admin schemas (billing.py)
+    "TierFeatureLimitEntry",
     "SubscriptionTierBase",
     "SubscriptionTierCreate",
     "SubscriptionTierUpdate",
     "SubscriptionTierResponse",
     "SubscriptionTierListResponse",
-    # Vendor Subscription schemas (billing.py)
-    "VendorSubscriptionResponse",
-    "VendorSubscriptionWithVendor",
-    "VendorSubscriptionListResponse",
-    "VendorSubscriptionCreate",
-    "VendorSubscriptionUpdate",
+    # Merchant Subscription Admin schemas (billing.py)
+    "MerchantSubscriptionAdminResponse",
+    "MerchantSubscriptionWithMerchant",
+    "MerchantSubscriptionListResponse",
+    "MerchantSubscriptionAdminCreate",
+    "MerchantSubscriptionAdminUpdate",
+    # Merchant Feature Override schemas (billing.py)
+    "MerchantFeatureOverrideEntry",
+    "MerchantFeatureOverrideResponse",
     # Billing History schemas (billing.py)
     "BillingHistoryResponse",
-    "BillingHistoryWithVendor",
+    "BillingHistoryWithMerchant",
     "BillingHistoryListResponse",
     # Checkout & Portal schemas (billing.py)
     "CheckoutRequest",
@@ -98,4 +99,7 @@ __all__ = [
     "PortalSessionResponse",
     # Stats schemas (billing.py)
     "SubscriptionStatsResponse",
+    # Feature Catalog schemas (billing.py)
+    "FeatureDeclarationResponse",
+    "FeatureCatalogResponse",
 ]