feat(ui): 添加全局Snackbar组件并替换局部实现

将原本分散在各组件的Snackbar功能统一为全局组件，通过Pinia store管理状态
移除CreateTemplateScreen中的局部Snackbar实现，改用全局组件
添加Snackbar store提供多种消息类型方法(success/error/warning/info)

src/renderer/App.vue

@@ -2,6 +2,7 @@
 import { DefaultLayout } from '@/renderer/components/layout'
 import GlobalDialog from '@/renderer/components/GlobalDialog.vue'
 import UpdateDialog from '@/renderer/components/UpdateDialog.vue'
+import GlobalSnackbar from '@/renderer/components/GlobalSnackbar.vue'
 import { onMounted } from 'vue'
 import { useAppStore } from '@/renderer/store/app'
 
@@ -75,6 +76,7 @@ const checkForUpdates = async () => {
   </DefaultLayout>
   <GlobalDialog />
   <UpdateDialog />
+  <GlobalSnackbar />
 </template>
 
 <style>