[Feature request] Support search in multiple pdf files ( maybe have same tag )

[dimayvegio]

First of all, thank you again for your contribution to creating such a great and easy-to-use self-hosted PDF reader.

I would like to suggest another feature based on my workflow. I often work on a single topic that has many related documents. In these cases, I usually need to search for a specific keyword across all documents related to that topic.

Therefore, it would be very useful for users like me if you could support searching for a keyword across multiple PDF files at once. Perhaps this could be done by allowing a search within all documents that share the same tag. This would make it much easier to quickly identify which PDF files I need to check for specific information.