Refactor AssistantPage layout for improved UI organization

Reorganized the AssistantPage layout by removing unnecessary div wrappers and enhancing the structure with SectionCard components for model and knowledge base configurations. This change improves readability and maintains a consistent design across the page.

src/components/pages/AssistantPage.tsx

@@ -705,21 +705,25 @@ export function AssistantPage() {
             title="模型配置"
             description="选择大语言模型和知识库能力"
           >
-            <div className="grid grid-cols-2 gap-4">
-              <SelectField
-                label="大语言模型"
-                value={form.model}
-                onChange={(value) => updateForm("model", value)}
-                options={["DeepSeek-V3", "Qwen-Max", "Kimi-K2", "Doubao-Pro", "GPT-4o"]}
-              />
+            <SelectField
+              label="大语言模型"
+              value={form.model}
+              onChange={(value) => updateForm("model", value)}
+              options={["DeepSeek-V3", "Qwen-Max", "Kimi-K2", "Doubao-Pro", "GPT-4o"]}
+            />
+          </SectionCard>
 
-              <SelectField
-                label="知识库"
-                value={form.knowledgeBase}
-                onChange={(value) => updateForm("knowledgeBase", value)}
-                options={["政务政策知识库", "售后知识库", "教育课程知识库", "医疗问答知识库"]}
-              />
-            </div>
+          <SectionCard
+            icon={<Database size={18} />}
+            title="知识库配置"
+            description="选择助手回答时可检索的业务知识来源"
+          >
+            <SelectField
+              label="知识库"
+              value={form.knowledgeBase}
+              onChange={(value) => updateForm("knowledgeBase", value)}
+              options={["政务政策知识库", "售后知识库", "教育课程知识库", "医疗问答知识库"]}
+            />
           </SectionCard>
 
           <SectionCard