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/Apps.vue

@@ -16,8 +16,25 @@
       />
     </div>
 
+    <!-- Loading Skeleton -->
+    <div v-if="!store.isConnected && sortedPackageEntries.length === 0" class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4 pb-6">
+      <div v-for="i in 3" :key="i" class="glass-card p-6 animate-pulse">
+        <div class="flex items-start gap-4">
+          <div class="w-16 h-16 rounded-lg bg-white/10"></div>
+          <div class="flex-1">
+            <div class="h-5 w-32 bg-white/10 rounded mb-2"></div>
+            <div class="h-4 w-48 bg-white/5 rounded mb-3"></div>
+            <div class="h-6 w-20 bg-white/5 rounded"></div>
+          </div>
+        </div>
+        <div class="mt-4 flex gap-2">
+          <div class="flex-1 h-9 bg-white/5 rounded-lg"></div>
+        </div>
+      </div>
+    </div>
+
     <!-- Empty State -->
-    <div v-if="sortedPackageEntries.length === 0 && !searchQuery" class="text-center py-16 pb-6">
+    <div v-else-if="sortedPackageEntries.length === 0 && !searchQuery" class="text-center py-16 pb-6">
       <div class="glass-card p-12 max-w-md mx-auto">
         <svg class="w-16 h-16 mx-auto text-white/40 mb-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
           <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M20 13V6a2 2 0 00-2-2H6a2 2 0 00-2 2v7m16 0v5a2 2 0 01-2 2H6a2 2 0 01-2-2v-5m16 0h-2.586a1 1 0 00-.707.293l-2.414 2.414a1 1 0 01-.707.293h-3.172a1 1 0 01-.707-.293l-2.414-2.414A1 1 0 006.586 13H4" />