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

frontend/src/documents/SelectionFloatingActions.tsx

@@ -12,10 +12,10 @@ import SelectionAssignmentMenu, { SelectionAssignmentMenuItem } from './Selectio
 import SelectionSummary from './SelectionSummary';
 import { useAppState } from '../app/appState';
 import { useWorkspaceSelectionContext } from '../app/WorkspaceSelectionContext';
+import type { DocumentId } from '../types/identifiers';
 
 const ROOT_FOLDER_LABEL = 'Documents';
 
-type DocumentId = string | number;
 type NullableDocumentId = DocumentId | null;
 
 type SelectedIdList = NullableDocumentId[] | null;
@@ -145,7 +145,7 @@ const buildTagAssignments = (
     return [];
   }
 
-  const map = new Map<string | number, {
+  const map = new Map<string, {
     id?: DocumentId;
     label: string;
     color: string | null;
@@ -209,7 +209,7 @@ const buildCorrespondentAssignments = (
     return [];
   }
 
-  const map = new Map<string | number, {
+  const map = new Map<string, {
     id?: DocumentId;
     label: string;
     count: number;
@@ -491,7 +491,7 @@ const SelectionFloatingActions: React.FC<SelectionFloatingActionsProps> = ({
       const value = isRecord(candidate)
         ? (candidate?.id ?? candidate?.value ?? null)
         : candidate;
-      if (!value && value !== 0) {
+      if (!value) {
         return;
       }
       await onMoveDocumentsToFolder(documentIdList, value as DocumentId);