Page editing, combining files into a new PDF, and a "don't keep documents" mode #90

What are you trying to do?

I use Folio as my everyday PDF reader and would like to also do basic document assembly in it, without a separate tool:

1. Delete individual pages, and insert pages from another PDF or from an image (for example a figure as PNG/JPEG).
2. Create a new PDF from several existing PDFs, images and Word documents.
3. Open sensitive documents without anything being kept on the computer. Folio currently stores a copy of the last 8 opened PDFs (up to 50 MB each), plus notes, chats, version history and reading position, in local storage.

What would help?

I've already built all three on top of 1.16.1 for my own use (I know the template asks to wait for agreement first; I'm sorry about that, I wanted to be sure the idea was workable before asking). I'm not asking you to merge it as is. I'd like to know whether you want any of it, and in what scope.

What it does:

1. Pages: in the Pages sidebar, right-click a page (or a selection) for Delete / Insert pages before / Insert pages after, plus two buttons under the list. The result is an edited in-memory copy that is exported with "Save copy", like content edits. The original file is untouched, version history records it ("Deleted pages", "Inserted pages"), and bookmarks follow their pages. Works with unsigned, unencrypted PDFs. Uses pdf-lib, which is already a dependency.
2. Create PDF from files: a dialog in the More menu to add several PDFs, PNG/JPEG images and Word documents, reorder them, and create one PDF. Each image becomes one A4 page. Word files go through the existing converter.
3. Don't keep documents: a switch in the More menu and in Settings > Storage. When on, nothing new is saved for documents opened from then on: no Recent copy, no notes/highlights, no chats, no version history, no reading position. Everything stays local and no network access is added.

How I checked: Windows only so far. I built the installer and used all three features by hand. tsc and npm run build pass. Logic for deleting, inserting and combining was checked on a sample PDF. npm run smoke fails on my machine in the highlight step (smoke-test.mjs:302), but it fails the same way on the unmodified 1.16.1 build, so I don't think it's related. I haven't tried macOS or Linux.

Scope options, whichever you prefer: one pull request with all three, or three separate pull requests (pages, combine files, privacy mode). I'll rebase on your current main first. Code was written with Claude Code; I tested it and am responsible for it.