e94e64ba6b
- Add backend endpoints: GET /dms/files, GET /dms/folders/{id}/files
- New SourceTree component: sources (Meine Dateien, Geteilte Ordner, Externe Speicher)
- New FileExplorer component: 5 view modes (list, table, icons-sm/md/lg)
- New FileDetails component: right panel with file metadata and actions
- Rewrite Dms.tsx: PluginToolbar + 3-column ResizablePanel layout
- Update DmsFile type: size_bytes + uploaded_by (backward compat aliases)
- Add 60+ i18n keys for de/en