fix(desktop): session persistence — refresh/login/context/empty-content 4-bug fix

1. App.tsx: add restoreSession() call on startup to prevent redirect
   to login page after refresh (isRestoring guard + BootstrapScreen)
2. CloneManager: call syncAgents() after loadClones() to restore
   currentAgent and conversation history on app load
3. zclaw-memory: add get_or_create_session() so frontend session UUID
   is persisted directly — kernel no longer creates mismatched IDs
4. openai.rs: assistant message content must be non-empty for
   Kimi/Qwen APIs — replace empty content with meaningful placeholders

Also includes admin-v2 ModelServices unified page (merge providers +
models + API keys into expandable row layout)

admin-v2/src/components/ErrorState.tsx

@@ -0,0 +1,51 @@
+import { Button, Result } from 'antd'
+import type { FallbackProps } from 'react-error-boundary'
+
+interface ErrorStateProps {
+  title?: string
+  message?: string
+  onRetry?: () => void
+}
+
+export function ErrorState({
+  title = '加载失败',
+  message,
+  onRetry,
+}: ErrorStateProps) {
+  return (
+    <div className="flex items-center justify-center min-h-[200px] p-8">
+      <Result
+        status="error"
+        title={title}
+        subTitle={message}
+        extra={
+          onRetry ? (
+            <Button type="primary" onClick={onRetry}>
+              重试
+            </Button>
+          ) : undefined
+        }
+      />
+    </div>
+  )
+}
+
+export function ErrorFallback({ error, resetErrorBoundary }: FallbackProps) {
+  return (
+    <div className="flex items-center justify-center min-h-[200px] p-8">
+      <Result
+        status="error"
+        title="页面出现错误"
+        subTitle={error.message}
+        extra={
+          <div className="flex gap-2">
+            <Button onClick={resetErrorBoundary}>重试</Button>
+            <Button type="primary" onClick={() => window.location.reload()}>
+              刷新页面
+            </Button>
+          </div>
+        }
+      />
+    </div>
+  )
+}