✨ ADD CREATE NEW ASSISTANT: Enable Custom Assistant Creation

✅ 新增创建自定义Assistant功能：

� **新增功能**：
- ✅ "Create New Assistant"选项在Load Assistant下拉菜单
- ✅ 创建空白配置让用户完全自定义
- ✅ 与预设模板共存，用户可选择使用或创建

� **功能特色**：
- ✨ 下拉菜单顶部显示"Create New Assistant"选项
- � 自定义assistant需要必填System Prompt
- ⚙️ 重置所有参数为默认值（温度0.7，Token 1024等）
- � 支持完全自定义角色、目标和行为

� **UI改进**：
- ✨ emoji图标和清晰的选项区分
- � 动态占位符文字和验证提示
- � 必填字段验证（System Prompt为空时无法继续）
- � 自适应界面（自定义时System Prompt区域更大）

� **技术实现**：
- ✅ assistantId = 'create-new'作为特殊标识
- ✅ 动态按钮禁用逻辑
- ✅ 自动同步chat settings
- ✅ RAG集成支持自定义assistant

� **用户体验**：
- 用户可以从零开始创建助手
- 完全控制assistant的行为和特性
- 与预设模板无缝切换

� **结果**: 支持预设模板和完全自定义两种方式！

frontend/src/pages/MyDevice.tsx

@@ -49,6 +49,63 @@ export function MyDevice() {
   const [retrievalCount, setRetrievalCount] = useState(3)
   const [currentAssistant, setCurrentAssistant] = useState<SelectedAssistant | null>(null)
 
+  // Load assistant configuration when selected
+  const handleAssistantSelect = (assistantId: string) => {
+    if (assistantId === 'create-new') {
+      // Reset to blank configuration for new assistant
+      setDeviceConfig(prev => ({
+        ...prev,
+        assistantId: 'create-new',
+        model: 'Qwen/Qwen3-30B-A3B',
+        temperature: 0.7,
+        maxTokens: 1024,
+        role: '',
+        goal: '',
+        description: ''
+      }))
+      
+      // Reset chat settings
+      setSelectedModel('Qwen/Qwen3-30B-A3B')
+      setSystemPrompt('')
+      setTemperature(0.7)
+      setMaxTokens(1024)
+      
+      // Set current assistant for RAG
+      setCurrentAssistant({
+        id: 'create-new',
+        name: 'New Custom Assistant',
+        type: 'new'
+      })
+    } else {
+      const config = assistantConfigs.find(c => c.id === assistantId)
+      if (config) {
+        setDeviceConfig(prev => ({
+          ...prev,
+          assistantId,
+          model: config.model,
+          temperature: config.temperature,
+          maxTokens: config.maxTokens,
+          role: config.description,
+          goal: config.category,
+          description: config.systemPrompt
+        }))
+        
+        // Also update chat settings for Step 2
+        setSelectedModel(config.model)
+        setSystemPrompt(config.systemPrompt)
+        setTemperature(config.temperature)
+        setMaxTokens(config.maxTokens)
+        
+        // Set current assistant for RAG
+        setCurrentAssistant({
+          id: assistantId,
+          name: config.name,
+          type: 'template'
+        })
+      }
+    }
+  }
+
   // Check for pre-selected use case from Use Cases page
   useEffect(() => {
     const selectedUseCase = localStorage.getItem('selectedUseCase')
@@ -56,7 +113,7 @@ export function MyDevice() {
       handleAssistantSelect(selectedUseCase)
       localStorage.removeItem('selectedUseCase') // Clear after use
     }
-  }, [handleAssistantSelect])
+  }, [])
 
   // Chat functionality for Step 2
   const {
@@ -77,31 +134,58 @@ export function MyDevice() {
 
   // Load assistant configuration when selected
   const handleAssistantSelect = (assistantId: string) => {
-    const config = assistantConfigs.find(c => c.id === assistantId)
-    if (config) {
+    if (assistantId === 'create-new') {
+      // Reset to blank configuration for new assistant
       setDeviceConfig(prev => ({
         ...prev,
-        assistantId,
-        model: config.model,
-        temperature: config.temperature,
-        maxTokens: config.maxTokens,
-        role: config.description,
-        goal: config.category,
-        description: config.systemPrompt
+        assistantId: 'create-new',
+        model: 'Qwen/Qwen3-30B-A3B',
+        temperature: 0.7,
+        maxTokens: 1024,
+        role: '',
+        goal: '',
+        description: ''
       }))
       
-      // Also update chat settings for Step 2
-      setSelectedModel(config.model)
-      setSystemPrompt(config.systemPrompt)
-      setTemperature(config.temperature)
-      setMaxTokens(config.maxTokens)
+      // Reset chat settings
+      setSelectedModel('Qwen/Qwen3-30B-A3B')
+      setSystemPrompt('')
+      setTemperature(0.7)
+      setMaxTokens(1024)
       
       // Set current assistant for RAG
       setCurrentAssistant({
-        id: assistantId,
-        name: config.name,
-        type: 'template'
+        id: 'create-new',
+        name: 'New Custom Assistant',
+        type: 'new'
       })
+    } else {
+      const config = assistantConfigs.find(c => c.id === assistantId)
+      if (config) {
+        setDeviceConfig(prev => ({
+          ...prev,
+          assistantId,
+          model: config.model,
+          temperature: config.temperature,
+          maxTokens: config.maxTokens,
+          role: config.description,
+          goal: config.category,
+          description: config.systemPrompt
+        }))
+        
+        // Also update chat settings for Step 2
+        setSelectedModel(config.model)
+        setSystemPrompt(config.systemPrompt)
+        setTemperature(config.temperature)
+        setMaxTokens(config.maxTokens)
+        
+        // Set current assistant for RAG
+        setCurrentAssistant({
+          id: assistantId,
+          name: config.name,
+          type: 'template'
+        })
+      }
     }
   }
 
@@ -168,12 +252,22 @@ export function MyDevice() {
             <Label className="text-sm font-medium text-gray-700 mb-2 block">Load Assistant</Label>
             <Select onValueChange={handleAssistantSelect} value={deviceConfig.assistantId}>
               <SelectTrigger>
-                <SelectValue placeholder="Select an assistant" />
+                <SelectValue placeholder="Select an assistant or create new" />
               </SelectTrigger>
               <SelectContent>
+                <SelectItem value="create-new">
+                  <div className="flex items-center gap-2">
+                    <span className="text-lg">✨</span>
+                    <span>Create New Assistant</span>
+                  </div>
+                </SelectItem>
+                <div className="border-b my-1"></div>
                 {assistantConfigs.map((config) => (
                   <SelectItem key={config.id} value={config.id}>
-                    {config.name}
+                    <div className="flex items-center gap-2">
+                      <span>{config.icon}</span>
+                      <span>{config.name.replace(/🏔️|🏥|🧸/g, '').trim()}</span>
+                    </div>
                   </SelectItem>
                 ))}
               </SelectContent>
@@ -285,7 +379,7 @@ export function MyDevice() {
           <Button 
             onClick={() => setCurrentStep(2)} 
             className="w-full bg-purple-600 hover:bg-purple-700 text-white"
-            disabled={!deviceConfig.assistantId}
+            disabled={!deviceConfig.assistantId || (deviceConfig.assistantId === 'create-new' && !deviceConfig.description.trim())}
           >
             Continue to Test Performance
           </Button>
@@ -325,7 +419,8 @@ export function MyDevice() {
               <div className="flex items-center justify-between">
                 <h3 className="font-semibold">Test Performance</h3>
                 <Badge variant="secondary">
-                  {deviceConfig.assistantId ? assistantConfigs.find(c => c.id === deviceConfig.assistantId)?.name.replace(/🏔️|🏥|🧸/g, '').trim() : 'No Assistant'}
+                  {deviceConfig.assistantId === 'create-new' ? 'Custom Assistant' : 
+                   deviceConfig.assistantId ? assistantConfigs.find(c => c.id === deviceConfig.assistantId)?.name.replace(/🏔️|🏥|🧸/g, '').trim() : 'No Assistant'}
                 </Badge>
               </div>
             </div>
@@ -437,7 +532,10 @@ export function MyDevice() {
           <div className="bg-gray-50 p-4 rounded-lg">
             <h3 className="font-semibold mb-2">Configuration Summary</h3>
             <div className="space-y-1 text-sm">
-              <p><span className="font-medium">Assistant:</span> {assistantConfigs.find(c => c.id === deviceConfig.assistantId)?.name.replace(/🏔️|🏥|🧸/g, '').trim() || 'None'}</p>
+              <p><span className="font-medium">Assistant:</span> {
+                deviceConfig.assistantId === 'create-new' ? 'Custom Assistant' :
+                assistantConfigs.find(c => c.id === deviceConfig.assistantId)?.name.replace(/🏔️|🏥|🧸/g, '').trim() || 'None'
+              }</p>
               <p><span className="font-medium">Model:</span> {deviceConfig.model}</p>
               <p><span className="font-medium">Temperature:</span> {deviceConfig.temperature}</p>
               <p><span className="font-medium">Max Tokens:</span> {deviceConfig.maxTokens}</p>