refactor(top-nav-bar): add custom back prop

- add customBack prop to enable explicit custom back handling
- rewrite back navigation logic to use the new prop instead of inferring from emit listeners
- remove unused getCurrentInstance import
- update three AIGC page components to use the custom-back prop

src/components/TopNavBar/index.vue

@@ -31,7 +31,7 @@
 </template>
 
 <script setup>
-import { computed, getCurrentInstance, onMounted, ref } from "vue";
+import { computed, onMounted, ref } from "vue";
 
 // 定义props
 const props = defineProps({
@@ -85,11 +85,14 @@ const props = defineProps({
     type: Boolean,
     default: false,
   },
+  customBack: {
+    type: Boolean,
+    default: false,
+  },
 });
 
 // 定义emits
 const emit = defineEmits(["back"]);
-const instance = getCurrentInstance();
 
 // 系统信息
 const statusBarHeight = ref(0);
@@ -145,25 +148,9 @@ const navContentStyle = computed(() => {
   };
 });
 
-const hasBackListener = computed(() => {
-  const vnodeProps = instance?.vnode?.props || {};
-  return Boolean(vnodeProps.onBack);
-});
-
 // 处理返回事件
 const handleBack = () => {
-  const pages = getCurrentPages();
-
-  if (pages.length <= 1) {
-    // #ifdef MP-WEIXIN
-    if (typeof wx !== "undefined" && typeof wx.exitMiniProgram === "function") {
-      wx.exitMiniProgram();
-      return;
-    }
-    // #endif
-  }
-
-  if (hasBackListener.value) {
+  if (props.customBack) {
     emit("back");
     return;
   }