fix(TopNavBar): update root page back navigation behavior

replace WeChat mini-program specific exit logic with uni.reLaunch to index page for consistent cross-platform behavior when at the root navigation stack

src/components/TopNavBar/index.vue

@@ -155,12 +155,10 @@ const handleBack = () => {
   const pages = getCurrentPages();
 
   if (pages.length <= 1) {
-    // #ifdef MP-WEIXIN
-    if (typeof wx !== "undefined" && typeof wx.exitMiniProgram === "function") {
-      wx.exitMiniProgram();
-      return;
-    }
-    // #endif
+    uni.reLaunch({
+      url: "/pages/index/index",
+    });
+    return;
   }
 
   if (hasBackListener.value) {