fix(security-audit): close prompt-audit bypass and privacy gaps

Stop WebSocket follow-up turns from reusing a request-wide audit cache, scan
client-controlled instruction fields, fail closed on stale weaker configs, and
tighten preview/SSRF controls including persisted request stage.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/features/prompt-audit/components/EventDetailDialog.vue

@@ -45,7 +45,8 @@
         <dt class="text-gray-500">Config</dt><dd>v{{ event.config_version }}</dd>
         <dt class="text-gray-500">Chunks</dt><dd>{{ event.chunk_total }}</dd>
         <dt class="text-gray-500">Latency</dt><dd>{{ event.latency_ms }} ms</dd>
-        <dt class="text-gray-500">Protocol</dt><dd>{{ event.snapshot.protocol }} · {{ event.snapshot.endpoint }} · {{ event.snapshot.stage }}</dd>
+        <dt class="text-gray-500">{{ t('admin.promptAudit.events.stage') }}</dt><dd>{{ event.snapshot.stage || 'http' }}</dd>
+        <dt class="text-gray-500">Protocol</dt><dd>{{ event.snapshot.protocol }} · {{ event.snapshot.endpoint }}</dd>
       </dl>
     </div>
   </BaseDialog>

frontend/src/features/prompt-audit/components/EventWorkspace.vue

@@ -79,7 +79,7 @@
             <td class="px-3 py-3 text-gray-700 dark:text-dark-200">{{ event.snapshot.group_name || '—' }}</td>
             <td class="px-3 py-3">
               <p class="font-medium text-gray-900 dark:text-white">{{ event.snapshot.endpoint }}</p>
-              <p class="mt-1 text-xs text-gray-500">{{ event.snapshot.model }} · {{ event.snapshot.protocol }}</p>
+              <p class="mt-1 text-xs text-gray-500">{{ event.snapshot.model }} · {{ event.snapshot.protocol }} · {{ event.snapshot.stage || 'http' }}</p>
             </td>
             <td class="px-3 py-3">
               <span class="rounded-full px-2 py-0.5 text-xs font-medium" :class="decisionClass(event.decision)">{{ event.decision }} · {{ event.risk_level }}</span>