fix: polish UX error handling across views (FINAL-01)

- AppDetails: replace alert() with dismissible toast, add error feedback
  for start/stop/restart/uninstall actions
- GoalDetail: add error toast for install failures instead of silent catch
- Apps: add loading skeleton when WebSocket data hasn't arrived yet
- Add appDetails.noLaunchUrl i18n key

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

neode-ui/src/views/AppDetails.vue

@@ -448,6 +448,16 @@
         </div>
       </div>
     </Transition>
+
+    <!-- Action error toast -->
+    <Transition name="fade">
+      <div v-if="actionError" class="fixed bottom-20 left-1/2 -translate-x-1/2 z-50 max-w-md w-full px-4" role="alert" aria-live="assertive">
+        <div class="bg-red-500/20 border border-red-500/40 backdrop-blur-sm rounded-lg px-4 py-3 text-red-200 text-sm flex items-center justify-between gap-3">
+          <span>{{ actionError }}</span>
+          <button @click="actionError = ''" :aria-label="t('apps.dismissError')" class="text-red-300 hover:text-white shrink-0">&times;</button>
+        </div>
+      </div>
+    </Transition>
   </div>
 </template>
 
@@ -574,6 +584,16 @@ const gatewayState = computed(() => {
   return gw ? gw.state : 'not installed'
 })
 
+// Action error toast
+const actionError = ref('')
+let errorTimer: ReturnType<typeof setTimeout> | undefined
+
+function showActionError(msg: string) {
+  actionError.value = msg
+  if (errorTimer) clearTimeout(errorTimer)
+  errorTimer = setTimeout(() => { actionError.value = '' }, 5000)
+}
+
 const uninstallModal = ref({
   show: false,
   appTitle: ''
@@ -783,8 +803,7 @@ function launchApp() {
   const lanConfig = pkg.value.manifest.interfaces?.main?.['lan-config']
   
   if (torAddress || lanConfig) {
-    // In development, just alert - in production would open the actual interface
-    alert(`Would launch ${pkg.value.manifest.title} interface`)
+    showActionError(t('appDetails.noLaunchUrl'))
   }
 }
 
@@ -792,7 +811,7 @@ async function startApp() {
   try {
     await store.startPackage(appId.value)
   } catch (err) {
-    if (import.meta.env.DEV) console.error('Failed to start app:', err)
+    showActionError(`Failed to start: ${err instanceof Error ? err.message : 'Unknown error'}`)
   }
 }
 
@@ -800,7 +819,7 @@ async function stopApp() {
   try {
     await store.stopPackage(appId.value)
   } catch (err) {
-    if (import.meta.env.DEV) console.error('Failed to stop app:', err)
+    showActionError(`Failed to stop: ${err instanceof Error ? err.message : 'Unknown error'}`)
   }
 }
 
@@ -808,7 +827,7 @@ async function restartApp() {
   try {
     await store.restartPackage(appId.value)
   } catch (err) {
-    if (import.meta.env.DEV) console.error('Failed to restart app:', err)
+    showActionError(`Failed to restart: ${err instanceof Error ? err.message : 'Unknown error'}`)
   }
 }
 
@@ -827,8 +846,7 @@ async function confirmUninstall() {
     await store.uninstallPackage(appId.value)
     router.push('/dashboard/apps').catch(() => {})
   } catch (err) {
-    if (import.meta.env.DEV) console.error('Failed to uninstall app:', err)
-    alert(t('common.error'))
+    showActionError(`Failed to uninstall: ${err instanceof Error ? err.message : 'Unknown error'}`)
   }
 }
 
@@ -893,4 +911,13 @@ function getStatusDotClass(state: PackageState): string {
   transform: scale(0.95);
   opacity: 0;
 }
+
+.fade-enter-active,
+.fade-leave-active {
+  transition: opacity 0.3s ease;
+}
+.fade-enter-from,
+.fade-leave-to {
+  opacity: 0;
+}
 </style>