feat: add functionality to manually split documents at specific pages via the UI and API

paperless-frontend/src/api/inbox.ts

@@ -19,6 +19,7 @@ export interface InboxFile {
   source: InboxSource;
   pageCount: number;
   deletedPages: number[];
+  manualSplitPages: number[];
   rotations: Record<string, number>;
   barcodes: InboxBarcode[];
   createdAt: string;
@@ -62,6 +63,9 @@ export const inboxApi = {
   remove: (id: string) =>
     api.delete(`/api/inbox/${encodeURIComponent(id)}`).then((r) => r.data),
 
+  toggleSplit: (id: string, page: number) =>
+    api.post(`/api/inbox/${encodeURIComponent(id)}/pages/${page}/split`).then(() => {}),
+
   removePage: (id: string, page: number) =>
     api
       .delete(`/api/inbox/${encodeURIComponent(id)}/pages/${page}`)