The signing tool keeps no signature on the device (#1, bau-pm BAU-260)

PDF.js's signature dialog saved every signature in localStorage under
pdfjs.signature, "save" ticked on every open, for this origin rather
than for a bau-pm user. Measured on v0.1.0: a typed and an uploaded
signature were offered to a fresh page on the same browser, the way the
next person on a shared tablet would get it, a Redmine logout included.
Another browser profile saw nothing; the server never had anything.

The glue's fifth duty, in every window before PDF.js's modules: delete
the store (a device that saved signatures loses them on its first
visit), refuse writes to that key, hold the save box unticked through a
property on the element and hide it, and hide the dialog's Bild tab and
its file picker, so a scanned signature never enters the dialog.

test/signatures.mjs is the second gate, in CI and the release workflow:
a browser seeded with a real saved entry (captured from v0.1.0's own
store) is offered none, the dialog shows neither the box nor the tab, a
typed signature is placed and not stored, a fresh page is offered
nothing. Fed v0.1.0: 9 findings, exit 1. Against this image: 0, and the
zero-host gate drove 117 tool pages with nothing leaving the origin. A
signed PDF still exports with the signature on the page.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -4,6 +4,18 @@ All notable changes to this project are documented in this file. The format is b
 
 ## [Unreleased]
 
+### Security
+
+- The signing tool keeps no signature on the device (issue #1, bau-pm BAU-260). PDF.js's signature dialog saved every signature in the browser's `localStorage`, with *Unterschrift speichern* ticked by default, for this address rather than for a bau-pm user, so the next person on a shared tablet or site office PC was offered the previous one's signature, typed, drawn or traced from an uploaded image, and logging out of bau-pm did not clear it. Every page now deletes that store and refuses its writes, and the dialog's save box is held unticked and hidden. Signatures a device saved before are deleted on its first visit after the update.
+
+### Removed
+
+- The *Bild* tab of the signing dialog, and its file picker: a scanned signature no longer enters the tool. Signing means typing or drawing it.
+
+### Added
+
+- A second gate, `test/signatures.mjs`, in CI and in the release workflow: nothing saved before is offered, nothing signed is stored, a fresh page is offered nothing, and the dialog shows neither the save box nor the image tab. Fed v0.1.0 it fails with 9 findings.
+
 ## [0.1.1] - 2026-10-24
 
 The same BentoPDF on current packages. Nothing in this repository's own code changed; what changed is that a build no longer ships whatever base image the runner happened to have cached, so this image carries nginx 1.31.8 where v0.1.0 carried 1.31.6. Out of bau-pm's v0.22.3 security review.