fix(license): shared invalid/grace banners + instance copy

Surface expired/over_instance/revoked red banners with CTAs via a
shared LicenseStatusBanners used by settings and ProGate. Hide seats
in product UI; keep HMAC dual-path and never silent-clear keys.

frontend/src/api/license/index.ts

@@ -3,7 +3,6 @@ import { http } from '../http'
 export interface LicenseInfo {
   plan: 'free' | 'pro'
   edition?: string
-  seats?: number
   instances?: number
   customer?: string
   expiresAt?: number
@@ -16,6 +15,8 @@ export interface LicenseInfo {
   graceDaysLeft?: number
   lastVerifiedAt?: number
   instanceId?: string
+  /** expired | over_instance | revoked — 非有效 Pro 时红条 */
+  invalidReason?: 'expired' | 'over_instance' | 'revoked' | string
 }
 export const licenseApi = {
   status: () => http.get<{ license: LicenseInfo; pro: boolean; features: string[] }>('/system/license'),