refactor: introduce dedicated identifier types for improved clarity and type safety

frontend/src/desktop/DesktopWorkspace.tsx

@@ -29,8 +29,7 @@ import '../styles/workspace/workspace-layout.css';
 import '../styles/workspace/workspace-items.css';
 import '../styles/workspace/workspace-cards.css';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
-
-type Identifier = string | number;
+import type { DocumentId, Identifier } from '../types/identifiers';
 
 type TagLike = { id?: Identifier | null; label?: string; color?: string | null } | null;
 type DocumentLinkLike = { url?: string | null; mimeType?: string | null };
@@ -79,7 +78,7 @@ interface DocumentSizeInfo {
 }
 
 interface PreviewMetadataEntry {
-  docId: string;
+  docId: DocumentId;
   width: number;
   height: number;
 }
@@ -225,7 +224,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
       const syntheticEvent = event || ({
         metaKey: true,
         ctrlKey: true,
-        preventDefault: () => {},
+        preventDefault: () => { },
       } as unknown as PointerEvent);
       docIds.forEach((id) => {
         const key = getDocRowKey(id);
@@ -354,7 +353,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
     engine.recalcVisibleDocIds();
   }, [engine]);
 
-  const setDraggingId = useCallback((value: string | number | null) => {
+  const setDraggingId = useCallback((value: string | null) => {
     engine.setDraggingId(value);
   }, [engine]);
 
@@ -686,7 +685,7 @@ const DesktopWorkspace: React.FC<DesktopWorkspaceProps> = ({
     },
     [resolvePreviewDimensions],
   );
- 
+
 
   useEffect(() => {
     if (draggingId && !items.some((doc) => String(doc.id) === draggingId)) {
@@ -1072,8 +1071,8 @@ function DesktopWorkspaceView({
               const dragging = docKey ? draggingId === docKey : false;
               const docTagKeys = Array.isArray(doc?.tags)
                 ? doc.tags
-                    .map((tag) => (tag?.id != null ? String(tag.id) : null))
-                    .filter((id): id is string => Boolean(id))
+                  .map((tag) => (tag?.id != null ? String(tag.id) : null))
+                  .filter((id): id is string => Boolean(id))
                 : [];
               const matchesFilter =
                 activeTagSet.size === 0 || docTagKeys.some((key) => activeTagSet.has(key));