[Feature Request] Highlight search terms inside the PDF viewer

Description When searching for documents, Paperless-ngx correctly returns matching documents and displays highlighted search snippets. However, after opening a document, it can be difficult to locate the actual occurrence of the search term within long PDFs or OCR-generated documents. Users often have to manually search the document again or scroll through multiple pages to find the relevant text. Proposed solution Highlight all search terms directly inside the integrated PDF viewer when a document is opened from the search results. Ideally this would include: Automatically highlight all matches in the document. Jump to the first match when the document opens. Navigation controls for Next and Previous match. Display the total number of matches (e.g. "3 of 12"). Preserve the current behavior when a document is opened without an active search. Benefits Much faster navigation in long documents. Better usability for OCR-heavy archives. Reduces the need to…