Add multi-select support to pmshare panel (#1779)

* Add multi-select support to share panel

- Replace single selection index with per-user selected flag
- Allow sending to multiple selected users
- Add sending state to prevent multiple clicks
- Update default selection logic to mark first user as selected

* 简化代码逻辑

* update

Signed-off-by: bggRGjQaUbCoE <githubaccount56556@proton.me>

---------

Signed-off-by: lesetong <oscarlbw@qq.com>
Co-authored-by: bggRGjQaUbCoE <githubaccount56556@proton.me>

lib/utils/page_utils.dart

@@ -62,7 +62,6 @@ abstract class PageUtils {
   }) async {
     // if (kDebugMode) debugPrint(content.toString());
 
-    int? selectedIndex;
     List<UserModel> userList = <UserModel>[];
 
     final shareListRes = await ImGrpc.shareList(size: 3);
@@ -77,11 +76,10 @@ abstract class PageUtils {
         ),
       );
     } else if (context.mounted) {
-      UserModel? userModel = await Navigator.of(context).push(
+      final UserModel? userModel = await Navigator.of(context).push(
         GetPageRoute(page: () => const ContactPage()),
       );
       if (userModel != null) {
-        selectedIndex = 0;
         userList.add(userModel);
       }
     }
@@ -92,7 +90,6 @@ abstract class PageUtils {
         builder: (context) => SharePanel(
           content: content,
           userList: userList,
-          selectedIndex: selectedIndex,
         ),
         useSafeArea: true,
         enableDrag: false,