[Feature Request] Merge Documents as Versions Instead of Combining Files

Description I would like to suggest an enhancement to the existing "Merge" functionality. Currently, the Merge action combines multiple selected documents into a single document (for example, multiple PDF files are merged into one PDF file). It would be useful to have an additional option that works differently: Instead of combining all files into one PDF document, the selected documents should be merged into a single Paperless-ngx document while keeping each original document as a separate version. Example Use Case Imagine having multiple versions of the same document over time: Contract_v1.pdf Contract_v2.pdf Contract_v3.pdf With the proposed functionality, Paperless-ngx would create one document entry containing all three versions: Version 1: Contract_v1.pdf Version 2: Contract_v2.pdf Version 3: Contract_v3.pdf Each original PDF file would remain available as its own version instead of being permanently combined into a single PDF file. Bene…