Slideshow folders can mix Word documents in with images

A slideshow folder now plays .docx files alongside images: a one-page
document is shown whole (letterboxed like a photo); a longer one fills
the width and scrolls smoothly top to bottom during its docInterval
(new slideshow.json key, default 2x interval). Word's ~$ lock files are
skipped; changed documents (by mtime) are re-read on the minute refresh.

- kiosk-app/docx-render.js: the docx-preview rendering now shared by
  docview.html and slideshow.html. Each render gets its own class prefix
  and keeps its styles in its own container, so two documents crossfading
  can't restyle each other. "One page" is judged by content fitting the
  paper height, not section count - docx-preview only starts a new
  section at explicit page breaks, so a long unbroken document is one
  tall section.
- Document bytes are fetched on demand: the page sets its title to a
  request, slideshow.js answers via executeJavaScript - only for a .docx
  in that slideshow's own current listing (no file-read API exposed to
  pages; the preload is shared by every site).

Tested with the real main.js on Electron 44.5.1 under Xvfb + Openbox on a
folder of 2 images + a 1-page and a long .docx (+ a ~$ lock file): order,
crossfades, whole-page fit, scroll to the end, lock file skipped; the
single-.docx site still renders. The request handler answered a listed
.docx and refused /etc/passwd, a listed image, and a .docx outside the
folder.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cjz8a58eB5P9sUweqd3NHm

Readme.md

@@ -197,14 +197,17 @@ The kiosk machine still needs a working internet connection (ethernet, or WiFi c
   instead of a web address and it's shown from the kiosk's own disk:
   HTML pages, PDFs (built-in viewer), images, and Word documents (below). Works offline. The file
   must be readable by the `kiosk` user.
-- **Image slideshow** - Enter a folder instead (e.g. `/home/kiosk/photos/`)
-  and its images (jpg, png, gif, webp, bmp, svg, avif) play full-screen in
-  file-name order with a crossfade, 10 seconds each. Images added to or
-  removed from the folder are picked up within a minute, no restart
-  needed. Optional `slideshow.json` in the folder:
-  `{"interval": 10, "shuffle": false, "fit": "contain", "transition": 1, "recursive": false}`
-  (`fit`: `contain` shows the whole image, `cover` fills the screen and
-  crops; `recursive` includes subfolders).
+- **Slideshow** - Enter a folder instead (e.g. `/home/kiosk/photos/`) and
+  its images (jpg, png, gif, webp, bmp, svg, avif) and Word documents
+  (`.docx`) play full-screen in file-name order with a crossfade - images
+  10 seconds each, documents 20. A one-page document is shown whole; a
+  longer one fills the width and scrolls slowly top to bottom during its
+  time. Files added, removed or changed are picked up within a minute, no
+  restart needed. Optional `slideshow.json` in the folder:
+  `{"interval": 10, "docInterval": 20, "shuffle": false, "fit": "contain", "transition": 1, "recursive": false}`
+  (`docInterval`: seconds per document; `fit`: `contain` shows the whole
+  image, `cover` fills the screen and crops; `recursive` includes
+  subfolders).
 - **Word documents** - A `.docx` path (e.g. `/home/kiosk/docs/menu.docx`)
   is rendered as pages (text, tables, images, lists), scaled to the screen
   width, via the bundled [docx-preview](https://github.com/VolodymyrBaydalka/docxjs)
@@ -1474,7 +1477,7 @@ full migration pass.
 - **All-in-one install ISO** (`iso/build-iso.sh`, or Actions → Build kiosk ISO): Ubuntu Server 26.04 plus the kiosk in one USB stick — the Ubuntu install, then `install.sh` automatically on first boot. Interactive, unattended, or fully automatic. See "All-in-One Install ISO" above.
 - **Offline installs** (`--offline`): the ISO carries every package (including CUPS printing and all printer drivers), Node.js 22, and prebuilt Electron/Web UI modules, so a kiosk installs with no internet. With internet it still installs current versions online. Addons → CUPS Printing (menu or Web UI) installs from the bundle by itself when offline.
 - **Local files as sites:** an absolute path (`/home/kiosk/docs/menu.pdf`) shows a local page, PDF or image; a folder (`/home/kiosk/photos/`) plays as a full-screen **image slideshow** that picks up added/removed images within a minute. Works in both the Sites menu and the Web UI.
-- **Word documents as sites:** a `.docx` path renders in the kiosk via docx-preview (~1 MB of JavaScript, bundled offline), updating when the file changes.
+- **Word documents as sites:** a `.docx` path renders in the kiosk via docx-preview (~1 MB of JavaScript, bundled offline), updating when the file changes. Slideshow folders can mix `.docx` documents in with images.
 - **Electron upgrade:** v42.x → v44.x (42 leaves Electron's support window when 45 ships). Existing kiosks move to it via Advanced → Upgrade.
 - **Fix:** the CUPS menu could report an installed CUPS as "not installed" (`dpkg -l | grep -q` failing under `set -o pipefail`).