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

lib/routing/app_routes.dart

@@ -7,6 +7,7 @@ import '../api/marianumcloud/talk/room/get_room_response.dart';
 import '../main.dart';
 import '../model/account_data.dart';
 import '../share_intent/pending_share.dart';
+import '../share_intent/remote_file_ref.dart';
 import '../state/app/modules/app_modules.dart';
 import '../state/app/modules/chat/bloc/chat_bloc.dart';
 import '../state/app/modules/chat_list/bloc/chat_list_bloc.dart';
@@ -46,11 +47,16 @@ class AppRoutes {
     BuildContext context,
     String localPath, {
     bool openExternal = false,
+    RemoteFileRef? remoteFile,
   }) {
     pushScreen(
       context,
       withNavBar: false,
-      screen: FileViewer(path: localPath, openExternal: openExternal),
+      screen: FileViewer(
+        path: localPath,
+        openExternal: openExternal,
+        remoteFile: remoteFile,
+      ),
     );
   }
 
@@ -106,7 +112,7 @@ class AppRoutes {
     pushScreen(
       context,
       withNavBar: false,
-      screen: ShareChatPicker(share: share),
+      screen: ShareChatPicker.forExternalShare(share: share),
     );
   }
 
@@ -114,7 +120,29 @@ class AppRoutes {
     pushScreen(
       context,
       withNavBar: false,
-      screen: ShareFolderPicker(share: share),
+      screen: ShareFolderPicker.forExternalShare(share: share),
+    );
+  }
+
+  static void openInternalShareToChat(
+    BuildContext context,
+    RemoteFileRef file,
+  ) {
+    pushScreen(
+      context,
+      withNavBar: false,
+      screen: ShareChatPicker.forInternalShare(file: file),
+    );
+  }
+
+  static void openInternalSaveToFolder(
+    BuildContext context,
+    RemoteFileRef file,
+  ) {
+    pushScreen(
+      context,
+      withNavBar: false,
+      screen: ShareFolderPicker.forInternalSave(file: file),
     );
   }