added a swipeable media gallery for chat and folder images and videos with server previews, on-demand originals and zoom, and marked document previews in chat so they no longer pass for photos

lib/view/pages/talk/widgets/chat_bubble.dart

@@ -5,6 +5,7 @@ import '../../../../api/marianumcloud/talk/chat/get_chat_response.dart';
 import '../../../../api/marianumcloud/talk/room/get_room_response.dart';
 import '../../../../extensions/date_time.dart';
 import '../../../../extensions/text.dart';
+import '../../../../routing/app_routes.dart';
 import '../../../../share_intent/remote_file_ref.dart';
 import '../../../../state/app/modules/chat/bloc/chat_bloc.dart';
 import '../../../../utils/downloads/download_job.dart';
@@ -14,6 +15,7 @@ import '../../../../widget/demo_restricted.dart';
 import '../../../../widget/downloads/download_trigger.dart';
 import '../data/chat_bubble_styles.dart';
 import '../data/chat_message.dart';
+import '../data/talk_gallery_source.dart';
 import 'answer_reference.dart';
 import 'bubble.dart';
 import 'chat_bubble_poll.dart';
@@ -192,9 +194,21 @@ class _ChatBubbleState extends State<ChatBubble>
     if (guardDemoAction(context)) return;
     if (isDownloading) {
       confirmCancelDownload();
-    } else {
-      _startFileDownload();
+      return;
     }
+    final galleryItem = galleryItemFromTalk(widget.bubbleData);
+    if (galleryItem != null) {
+      AppRoutes.openMediaGallery(
+        context,
+        source: TalkGallerySource(
+          token: widget.chatData.token,
+          initial: galleryItem,
+        ),
+        initialKey: galleryItem.key,
+      );
+      return;
+    }
+    _startFileDownload();
   }
 
   void _updateMessage(BuildContext context) {