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/share_intent/share_target_page.dart

@@ -88,7 +88,7 @@ class ShareTargetPage extends StatelessWidget {
                   ),
                   ListTile(
                     leading: const Icon(Icons.chat_bubble_outline),
-                    title: const Text('An Chat senden'),
+                    title: const Text('An Talk-Chat senden'),
                     subtitle: const Text(
                       'Datei oder Text in einem Talk-Chat teilen',
                     ),
@@ -98,11 +98,11 @@ class ShareTargetPage extends StatelessWidget {
                   ),
                   ListTile(
                     enabled: share.hasFiles,
-                    leading: const Icon(Icons.folder_outlined),
-                    title: const Text('In Dateien speichern'),
+                    leading: const Icon(Icons.cloud_outlined),
+                    title: const Text('In Cloud speichern'),
                     subtitle: Text(
                       share.hasFiles
-                          ? 'In einen Nextcloud-Ordner hochladen'
+                          ? 'In einen Cloud-Ordner hochladen'
                           : 'Nur für Dateien verfügbar',
                     ),
                     trailing: const Icon(Icons.chevron_right),