feat: Add 添加SignupModal组件，并在CourseManage中集成注册功能；

src/components/signup/SignupModal.vue

@@ -596,7 +596,7 @@ export default {
 .right1 {
   border-left: 1px solid #f2f6fe;
   margin-left: 20px;
-  min-width: 200px;
+  max-width: 200px;
 
   .onerow {
     display: flex;
@@ -635,7 +635,7 @@ export default {
       width: 64px;
       height: 24px;
       margin-top: 25px;
-      margin-right: 25px;
+      margin-right: 18px;
       display: flex;
       align-items: center;
       justify-content: center;

src/views/course/CourseManage.vue

@@ -592,6 +592,7 @@ export default {
       tabName: "second",
       audienceDialogVisible: false,
       addSignupVisible: false,
+      selectedAudiences: [],
       learningSituation: {
         pageIndex: 1, //第几页
         pageSize: 10, // 每页多少条