Remove flutter chat (#26)

Had to squash merge manually as Forgejo was erroring

lib/models/info/audio.dart

@@ -0,0 +1,17 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+import "package:nexus/models/ms_duration.dart";
+part "audio.freezed.dart";
+part "audio.g.dart";
+
+@freezed
+abstract class AudioInfo with _$AudioInfo {
+  /// Information for images, [size] is in bytes.
+  const factory AudioInfo({
+    @MSDuration() Duration? duration,
+    @JsonKey(name: "mimetype") String? mimeType,
+    int? size,
+  }) = _AudioInfo;
+
+  factory AudioInfo.fromJson(Map<String, Object?> json) =>
+      _$AudioInfoFromJson(json);
+}