feat: 优化暗色主题样式，将原生select替换为el-select

- 优化el-select组件的暗色主题样式，包括输入框、下拉菜单、选中状态等
- 在Agents、MCP、ModelAPIs页面中将原生select替换为Element Plus el-select组件
- 提升UI一致性和用户体验

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/views/MCP.vue

@@ -890,15 +890,12 @@ const statusClass = (status: string) => {
           class="w-full bg-dark-600 border border-dark-500 rounded-lg py-2 pl-10 pr-4 text-white placeholder-gray-500 focus:outline-none focus:border-primary-orange"
         >
       </div>
-      <select
-        v-model="filterStatus"
-        class="bg-dark-600 border border-dark-500 rounded-lg px-4 py-2 text-white focus:outline-none focus:border-primary-orange"
-      >
-        <option value="all">All Status</option>
-        <option value="running">Running</option>
-        <option value="stopped">Stopped</option>
-        <option value="error">Error</option>
-      </select>
+      <el-select v-model="filterStatus" placeholder="Select" class="w-40" size="large">
+        <el-option label="All Status" value="all" />
+        <el-option label="Running" value="running" />
+        <el-option label="Stopped" value="stopped" />
+        <el-option label="Error" value="error" />
+      </el-select>
     </div>
 
     <div class="bg-dark-700 rounded-xl overflow-hidden">
@@ -987,16 +984,13 @@ const statusClass = (status: string) => {
 
             <div>
               <label class="block text-sm font-medium text-gray-300 mb-2">Type</label>
-              <select
-                v-model="editForm.type"
-                class="w-full bg-dark-600 border border-dark-500 rounded-lg px-4 py-2.5 text-white focus:outline-none focus:border-primary-orange"
-              >
-                <option value="Linear">Linear</option>
-                <option value="Google Maps">Google Maps</option>
-                <option value="File System">File System</option>
-                <option value="PostgreSQL">PostgreSQL</option>
-                <option value="GitHub">GitHub</option>
-              </select>
+              <el-select v-model="editForm.type" placeholder="Select" class="w-full" size="large">
+                <el-option label="Linear" value="Linear" />
+                <el-option label="Google Maps" value="Google Maps" />
+                <el-option label="File System" value="File System" />
+                <el-option label="PostgreSQL" value="PostgreSQL" />
+                <el-option label="GitHub" value="GitHub" />
+              </el-select>
             </div>
 
             <div>