fix: note/file move ops, rename/move atomicity, importDir folder creation

- importDir: create physical folder for imported directories
- RenameNode/MoveNode: os.Rename before DB updates (atomicity)
- RenameNode note/file: fail if physical file missing
- MoveNode: file renames before DB updates
- applyRemoteNoteOp: handle OpMove for notes/files
- applyRemoteNodeMove: handle notes/files with empty FsPath
- MoveNode sync payload: no fs_path for notes/files
- Add 7 tests covering all fixes

internal/core/files/file.go

@@ -526,6 +526,11 @@ func (s *Service) importDir(parentID, sourcePath, dirName string, copyMode bool)
 	}
 	_ = s.nodes.UpdateFsPath(folderNode.ID, folderFsPath)
 
+	physPath := filepath.Join(s.vaultRoot, folderFsPath)
+	if err := os.MkdirAll(physPath, 0o750); err != nil {
+		return nil, fmt.Errorf("create folder for imported dir: %w", err)
+	}
+
 	entries, err := os.ReadDir(sourcePath)
 	if err != nil {
 		return nil, err