implemented internal file sharing and saving, added server-side file references, refactored share pickers for unified flows, and updated UI branding labels

lib/view/pages/files/widgets/file_element.dart

@@ -7,6 +7,7 @@ import '../../../../api/marianumcloud/webdav/webdav_api.dart';
 import '../../../../extensions/date_time.dart';
 import '../../../../model/endpoint_data.dart';
 import '../../../../routing/app_routes.dart';
+import '../../../../share_intent/remote_file_ref.dart';
 import '../../../../utils/download_manager.dart';
 import '../../../../utils/file_clipboard.dart';
 import '../../../../widget/centered_leading.dart';
@@ -71,7 +72,11 @@ class _FileElementState extends State<FileElement> {
     if (status is DownloadDone) {
       DownloadManager.instance.clear(widget.file.path);
       _detachJob();
-      AppRoutes.openFileViewer(context, status.localPath);
+      AppRoutes.openFileViewer(
+        context,
+        status.localPath,
+        remoteFile: RemoteFileRef.fromCacheable(widget.file),
+      );
       setState(() {});
     } else if (status is DownloadFailed) {
       final message = status.message;
@@ -299,6 +304,18 @@ class _FileElementState extends State<FileElement> {
             _putOnClipboard(copy: true);
           },
         ),
+        if (!widget.file.isDirectory)
+          ListTile(
+            leading: const CenteredLeading(Icon(Icons.chat_bubble_outline)),
+            title: const Text('Im Talk-Chat teilen'),
+            onTap: () {
+              Navigator.of(sheetCtx).pop();
+              AppRoutes.openInternalShareToChat(
+                context,
+                RemoteFileRef.fromCacheable(widget.file),
+              );
+            },
+          ),
         ListTile(
           leading: const CenteredLeading(Icon(Icons.delete_outline)),
           title: const Text('Löschen'),