feat: Plan-based feature permissions and quota enforcement

Backend:
- Add HasQuota() permission factory for quota limits (resources, users, services, appointments, email templates, automated tasks)
- Add HasFeaturePermission() factory for feature-based permissions (SMS, masked calling, custom domains, white label, plugins, webhooks, calendar sync, analytics)
- Add has_feature() method to Tenant model for flexible permission checking
- Add new tenant permission fields: can_create_plugins, can_use_webhooks, can_use_calendar_sync, can_export_data
- Create Data Export API with CSV/JSON support for appointments, customers, resources, services
- Create Analytics API with dashboard, appointments, revenue endpoints
- Add calendar sync views and URL configuration

Frontend:
- Add usePlanFeatures hook for checking feature availability
- Add UpgradePrompt components (inline, banner, overlay variants)
- Add LockedSection wrapper and LockedButton for feature gating
- Update settings pages with permission checks

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/types.ts

@@ -31,6 +31,22 @@ export interface CustomDomain {
   verified_at?: string;
 }
 
+export interface PlanPermissions {
+  sms_reminders: boolean;
+  webhooks: boolean;
+  api_access: boolean;
+  custom_domain: boolean;
+  white_label: boolean;
+  custom_oauth: boolean;
+  plugins: boolean;
+  export_data: boolean;
+  video_conferencing: boolean;
+  two_factor_auth: boolean;
+  masked_calling: boolean;
+  pos_system: boolean;
+  mobile_app: boolean;
+}
+
 export interface Business {
   id: string;
   name: string;
@@ -63,6 +79,8 @@ export interface Business {
   resourceTypes?: ResourceTypeDefinition[]; // Custom resource types
   // Platform-controlled permissions
   canManageOAuthCredentials?: boolean;
+  // Plan permissions (what features are available based on subscription)
+  planPermissions?: PlanPermissions;
 }
 
 export type UserRole = 'superuser' | 'platform_manager' | 'platform_support' | 'owner' | 'manager' | 'staff' | 'resource' | 'customer';