feat(mcp): show wizard button only in custom mode

- Hide 'Use Configuration Wizard' button when preset MCP is selected
- Show wizard button only in custom mode or edit mode
- Prevents user confusion by avoiding wizard access when preset configs are loaded

src/i18n/locales/en.json

@@ -345,7 +345,7 @@
       "deleteMessage": "Are you sure you want to delete MCP server \"{{id}}\"? This action cannot be undone."
     },
     "presets": {
-      "title": "Presets",
+      "title": "Select MCP Type",
       "enable": "Enable",
       "enabled": "Enabled",
       "installed": "Installed",

src/i18n/locales/zh.json

@@ -345,7 +345,7 @@
       "deleteMessage": "确定要删除 MCP 服务器 \"{{id}}\" 吗？此操作无法撤销。"
     },
     "presets": {
-      "title": "预设库",
+      "title": "选择 MCP 类型",
       "enable": "启用",
       "enabled": "已启用",
       "installed": "已安装",