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/pages/Login.tsx

@@ -6,13 +6,11 @@ import { useState } from 'react'
 import { useNavigate, useSearchParams } from 'react-router-dom'
 import { LoginForm, ProFormText } from '@ant-design/pro-components'
 import { LockOutlined, UserOutlined, SafetyOutlined } from '@ant-design/icons'
-import { message, Divider, Typography } from 'antd'
+import { message } from 'antd'
 import { authService } from '@/services/auth'
 import { useAuthStore } from '@/stores/authStore'
 import type { LoginRequest } from '@/types'
 
-const { Title, Text } = Typography
-
 export default function Login() {
   const navigate = useNavigate()
   const [searchParams] = useSearchParams()
@@ -50,51 +48,75 @@ export default function Login() {
   }
 
   return (
-    <div style={{ minHeight: '100vh', display: 'flex' }}>
-      {/* 左侧品牌区 */}
-      <div
-        style={{
-          flex: '1 1 0',
-          display: 'flex',
-          flexDirection: 'column',
-          alignItems: 'center',
-          justifyContent: 'center',
-          background: 'linear-gradient(135deg, #001529 0%, #003a70 50%, #001529 100%)',
-          position: 'relative',
-          overflow: 'hidden',
-        }}
+    <div className="min-h-screen flex">
+      {/* Left Brand Panel — hidden on mobile */}
+      <div className="hidden md:flex flex-1 flex-col items-center justify-center relative overflow-hidden"
+        style={{ background: 'linear-gradient(135deg, #0c0a09 0%, #1c1917 40%, #292524 100%)' }}
       >
-        <Title level={1} style={{ color: '#fff', marginBottom: 8, letterSpacing: 4 }}>
-          ZCLAW
-        </Title>
-        <Text style={{ color: 'rgba(255,255,255,0.65)', fontSize: 16 }}>AI Agent 管理平台</Text>
-        <Divider style={{ borderColor: 'rgba(22,119,255,0.3)', width: 100, minWidth: 100 }} />
-        <Text style={{ color: 'rgba(255,255,255,0.45)', fontSize: 13, maxWidth: 320, textAlign: 'center' }}>
-          统一管理 AI 服务商、模型配置、API 密钥、用量监控与系统配置
-        </Text>
+        {/* Decorative gradient orb */}
+        <div
+          className="absolute w-[400px] h-[400px] rounded-full opacity-20 blur-3xl"
+          style={{ background: 'linear-gradient(135deg, #863bff, #47bfff)', top: '20%', left: '10%' }}
+        />
+        <div
+          className="absolute w-[300px] h-[300px] rounded-full opacity-10 blur-3xl"
+          style={{ background: 'linear-gradient(135deg, #47bfff, #863bff)', bottom: '10%', right: '15%' }}
+        />
+
+        {/* Brand content */}
+        <div className="relative z-10 text-center px-8">
+          <div
+            className="inline-flex items-center justify-center w-16 h-16 rounded-2xl mb-6"
+            style={{ background: 'linear-gradient(135deg, #863bff, #47bfff)' }}
+          >
+            <span className="text-white text-2xl font-bold">Z</span>
+          </div>
+          <h1 className="text-4xl font-bold text-white mb-3 tracking-tight">ZCLAW</h1>
+          <p className="text-white/50 text-base mb-8">AI Agent 管理平台</p>
+          <div className="w-16 h-px mx-auto mb-8" style={{ background: 'linear-gradient(90deg, transparent, #863bff, #47bfff, transparent)' }} />
+          <p className="text-white/30 text-sm max-w-sm mx-auto leading-relaxed">
+            统一管理 AI 服务商、模型配置、API 密钥、用量监控与系统配置
+          </p>
+        </div>
       </div>
 
-      {/* 右侧登录表单 */}
-      <div
-        style={{
-          flex: '0 0 480px',
-          display: 'flex',
-          alignItems: 'center',
-          justifyContent: 'center',
-          padding: 48,
-        }}
-      >
-        <div style={{ width: '100%', maxWidth: 360 }}>
-          <Title level={3} style={{ marginBottom: 4 }}>登录</Title>
-          <Text type="secondary" style={{ display: 'block', marginBottom: 32 }}>
+      {/* Right Login Form */}
+      <div className="flex-1 md:flex-none md:w-[480px] flex items-center justify-center p-8 bg-white dark:bg-neutral-950">
+        <div className="w-full max-w-[360px]">
+          {/* Mobile logo (visible only on mobile) */}
+          <div className="md:hidden flex items-center gap-3 mb-10">
+            <div
+              className="flex items-center justify-center w-10 h-10 rounded-xl"
+              style={{ background: 'linear-gradient(135deg, #863bff, #47bfff)' }}
+            >
+              <span className="text-white font-bold">Z</span>
+            </div>
+            <span className="text-xl font-bold text-neutral-900 dark:text-white">ZCLAW</span>
+          </div>
+
+          <h2 className="text-2xl font-semibold text-neutral-900 dark:text-white mb-1">
+            登录
+          </h2>
+          <p className="text-sm text-neutral-500 dark:text-neutral-400 mb-8">
             输入您的账号信息以继续
-          </Text>
+          </p>
 
           <LoginForm
             onFinish={handleSubmit}
             submitter={{
               searchConfig: { submitText: '登录' },
-              submitButtonProps: { loading, block: true },
+              submitButtonProps: {
+                loading,
+                block: true,
+                style: {
+                  height: 44,
+                  borderRadius: 8,
+                  fontWeight: 500,
+                  fontSize: 15,
+                  background: 'linear-gradient(135deg, #863bff, #47bfff)',
+                  border: 'none',
+                },
+              },
             }}
           >
             <ProFormText