feat(mobile): Add people list to exit bottom sheet (#6717)

* feat(mobile): Define constants as 'const'

* feat(mobile): Add people list to asset bottom sheet

Add a list of people per asset in the exif bottom sheet, like on the
web.

Currently the list of people is loaded by making a request each time to
the server. This is the MVP approach.
In the future, the people information can be synced like we're doing
with the assets.

* styling

---------

Co-authored-by: Alex Tran <alex.tran1502@gmail.com>

mobile/lib/modules/asset_viewer/providers/asset_people.provider.dart

@@ -0,0 +1,51 @@
+import 'package:immich_mobile/shared/models/asset.dart';
+import 'package:immich_mobile/shared/services/asset.service.dart';
+import 'package:logging/logging.dart';
+import 'package:openapi/api.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+part 'asset_people.provider.g.dart';
+
+/// Maintains the list of people for an asset.
+@riverpod
+class AssetPeopleNotifier extends _$AssetPeopleNotifier {
+  final log = Logger('AssetPeopleNotifier');
+
+  @override
+  Future<List<PersonWithFacesResponseDto>> build(Asset asset) async {
+    if (!asset.isRemote) {
+      return [];
+    }
+
+    final list = await ref
+        .watch(assetServiceProvider)
+        .getRemotePeopleOfAsset(asset.remoteId!);
+    if (list == null) {
+      return [];
+    }
+
+    // explicitly a sorted slice to make it deterministic
+    // named people will be at the beginning, and names are sorted
+    // ascendingly
+    list.sort((a, b) {
+      final aNotEmpty = a.name.isNotEmpty;
+      final bNotEmpty = b.name.isNotEmpty;
+      if (aNotEmpty && !bNotEmpty) {
+        return -1;
+      } else if (!aNotEmpty && bNotEmpty) {
+        return 1;
+      } else if (!aNotEmpty && !bNotEmpty) {
+        return 0;
+      }
+
+      return a.name.compareTo(b.name);
+    });
+    return list;
+  }
+
+  Future<void> refresh() async {
+    // invalidate the state – this way we don't have to
+    // duplicate the code from build.
+    ref.invalidateSelf();
+  }
+}