feat: improve mobile screen reader accessibility (#17876)

* WIP: adding screen reader support to mobile

* implemented getAltText

* implemented alt text solution that stores the alt text in the DB, which isn't really great

* moved alt text computation to immich_thumbnail.dart

* added unit tests

* revert unintended changes

* Added text to remaining buttons in Photo page

* fixed import

* Fixed issue of easy_localization not parsing select blocks

* Transferred the new screen reader help to web frontend

* remove unused property

* npm run format:fix

* code review

* revert unwanted change

* dart fmt

* revert web changes

---------

Co-authored-by: shenlong-tanwen <139912620+shalong-tanwen@users.noreply.github.com>

mobile/lib/widgets/asset_grid/group_divider_title.dart

@@ -1,3 +1,4 @@
+import 'package:easy_localization/easy_localization.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
@@ -74,10 +75,14 @@ class GroupDividerTitle extends HookConsumerWidget {
                 ? Icon(
                     Icons.check_circle_rounded,
                     color: context.primaryColor,
+                    semanticLabel:
+                        "unselect_all_in".tr(namedArgs: {"group": text}),
                   )
                 : Icon(
                     Icons.check_circle_outline_rounded,
                     color: context.colorScheme.onSurfaceSecondary,
+                    semanticLabel:
+                        "select_all_in".tr(namedArgs: {"group": text}),
                   ),
           ),
         ],