fix(frontend): correct integrations redirect tab and lazy-load panels

Map legacy section=integrations to tab=im instead of an invalid tab value,
and mount only the active IntegrationsModal tab to avoid duplicate API calls.

frontend/src/views/agent/AgentList.vue

@@ -1129,9 +1129,10 @@ const checkAndOpenEditModal = () => {
   const editId = route.query.edit as string
   const section = route.query.section as string
   if (editId && (section === 'im' || section === 'embed' || section === 'integrations')) {
+    const tab = section === 'embed' ? 'embed' : 'im'
     router.replace({
       path: '/platform/integrations',
-      query: { tab: section, agentId: editId },
+      query: { tab, agentId: editId },
     })
     return
   }

frontend/src/views/integrations/IntegrationsModal.vue

@@ -30,7 +30,7 @@
 
             <div class="settings-content">
               <div class="content-wrapper">
-                <div v-show="currentSection === 'im'" class="section">
+                <div v-if="currentSection === 'im'" class="section">
                   <div class="section-header">
                     <h2>{{ $t('agentEditor.im.title') }}</h2>
                     <p class="section-description">
@@ -49,7 +49,7 @@
                   <IMChannelPanel tenant-mode :initial-agent-id="initialAgentId" />
                 </div>
 
-                <div v-show="currentSection === 'embed'" class="section">
+                <div v-if="currentSection === 'embed'" class="section">
                   <div class="section-header">
                     <h2>{{ $t('agentEditor.embed.title') }}</h2>
                     <p class="section-description">{{ $t('agentEditor.embed.description') }}</p>