feat(aigc): add shared work top bar and back fixes

- add leftAction prop to AigcTopBar to switch between back arrow and home icon
- pass source=sharedWork query param when reLaunching home from shared work page
- update home page to detect shared work source, adjust top bar and back behavior
- add CSS styling for home top bar icon
- update root page back handler to exit WeChat mini program

src/components/TopNavBar/index.vue

@@ -152,6 +152,17 @@ const hasBackListener = computed(() => {
 
 // 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) {
     emit("back");
     return;