feat(security): harden gateway boundaries and usage policies

Consolidate subscription usage policy enforcement, privacy-safe persistence, and gateway security hardening into one reviewable change.

Includes bounded HTTP and execution envelopes, header and protocol guards, DNS and relay validation, authentication and secret projection hardening, secure backup/install paths, and regression coverage.

frontend/src/features/users/components/UserPlanDialog.vue

@@ -24,7 +24,7 @@
 
     <div class="max-h-[64vh] space-y-4 overflow-y-auto">
       <div class="rounded-lg border border-amber-500/20 bg-amber-500/10 px-3 py-2.5 text-xs text-amber-100/90">
-        {{ legacyT('后台发放会立即生效；如果新套餐包含每日额度或会员权益，用户已有的同类旧套餐会自动失效。') }}
+        {{ legacyT('后台发放会立即生效；新旧套餐包含同类每日额度、同类会员权益或同名互斥组时，旧套餐整包失效。') }}
       </div>
 
       <section class="space-y-2.5">
@@ -79,8 +79,8 @@
                 </div>
                 <div class="mt-2 flex flex-wrap gap-1.5">
                   <Badge
-                    v-for="label in entitlementLabels(item.entitlements)"
-                    :key="label"
+                    v-for="(label, index) in entitlementLabels(item.entitlements)"
+                    :key="`${label}-${index}`"
                     variant="outline"
                     class="h-5 px-1.5 py-0 text-[10px]"
                   >
@@ -115,7 +115,7 @@
             {{ legacyT('发放套餐') }}
           </h4>
           <p class="text-xs text-muted-foreground">
-            {{ legacyT('仅发放套餐权益，不产生用户付款；同类旧套餐会按现有规则自动替换。') }}
+            {{ legacyT('仅发放套餐权益，不产生用户付款；命中同类权益或同名互斥组时，冲突的旧套餐会整包失效。') }}
           </p>
         </div>