ab show loading LinearProgressIndicator (#7538)

* Display the LinearProgressIndicator at the top of ab if the current ab is both empty and in a loading state.
* Add pull error like the legacy ab.
* When forcefully reading the 'ab' list, retrieve the personal ab guid to judge the current mode  to prevent server upgrades while the main window remains open

Signed-off-by: 21pages <pages21@163.com>

flutter/lib/common/widgets/address_book.dart

@@ -48,6 +48,10 @@ class _AddressBookState extends State<AddressBook> {
         } else {
           return Column(
             children: [
+              // NOT use Offstage to wrap LinearProgressIndicator
+              if (gFFI.abModel.currentAbLoading.value &&
+                  gFFI.abModel.currentAbEmpty)
+                const LinearProgressIndicator(),
               buildErrorBanner(context,
                   loading: gFFI.abModel.currentAbLoading,
                   err: gFFI.abModel.currentAbPullError,