feat: add collapsible welcome and sticky tabs

Wrap the home welcome component in a collapsible container with smooth transitions. Implement scroll-based collapse and expand logic for the banner in the chat main list. Add sticky tab header styling and updated page layout for the discovery page.

src/pages/Discovery/index.vue

@@ -1,6 +1,6 @@
 <template>
-  <view class="flex flex-col h-full overflow-hidden min-height-0">
-    <view class="flex-shrink-0">
+  <view class="discovery-content">
+    <view class="discovery-tabs-sticky">
       <FindTabs v-if="discoveryTabs.length > 0" v-model="activeIndex" :tabs="discoveryTabs" @change="handleTabChange" />
     </view>
 
@@ -206,4 +206,18 @@ onMounted(() => {
 
 </script>
 
-<style lang="scss" scoped></style>
+<style lang="scss" scoped>
+.discovery-content {
+  width: 100%;
+  min-height: 100%;
+  background: $theme-color-50;
+}
+
+.discovery-tabs-sticky {
+  position: sticky;
+  top: 0;
+  z-index: 12;
+  width: 100%;
+  background: $theme-color-50;
+}
+</style>