Folder image slideshow sites; Electron 42 -> 44

Slideshow: a site whose path is a local folder (/home/kiosk/photos/, or
any existing directory) plays its images full-screen instead of showing
Chromium's directory listing. kiosk-app/slideshow.js maps the folder URL
to slideshow.html (resolveSiteUrl - used where main.js loads a view and
where attachView re-checks the configured URL) and pushes the image list
into the page from the main process (the page has no fs access), re-read
every minute so added/removed images show up without a restart. Natural
file-name order, crossfade, letterboxed by default; optional
slideshow.json in the folder: interval, shuffle, fit, transition,
recursive. provision_install_app already copies kiosk-app/*.js/*.html,
so new installs and Advanced -> Upgrade pick it up.

Electron: ^42.0.0 -> ^44.0.0. Electron supports the latest three majors
(44/43/42), so 42 drops out when 45 ships. Checked the 43/44 breaking
changes against kiosk-app: nothing it uses changed (no clipboard,
safeStorage, net.request, utilityProcess; BrowserView is deprecated but
still present through 46). The offline bundle builder now retries
Electron's install.js download, which crashes outright if a large
download is cut off mid-stream.

Tested with the real main.js on Electron 44.5.1 under Xvfb + Openbox:
slideshow fills the screen, cycles in order (01, 02, 10) skipping a .txt
file, honours slideshow.json, and an image added mid-run joined the
rotation after the refresh. Offline bundle rebuilt with Electron 44.5.1.

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

iso/offline/build-bundle.sh

@@ -185,7 +185,14 @@ build_modules() {
     # postinstall since ~v42) - lib/electron.sh runs this same install.js
     # on the target when online; offline it has to already be in dist/.
     if [[ -f "$tmp/node_modules/electron/install.js" ]]; then
-        (cd "$tmp" && node node_modules/electron/install.js) || die "Electron binary download failed"
+        # Retried: a large download cut off mid-stream crashes it outright.
+        local try
+        for try in 1 2 3; do
+            (cd "$tmp" && node node_modules/electron/install.js) && break
+            (( try < 3 )) || die "Electron binary download failed (3 attempts)"
+            info "Electron download failed - retrying ($((try + 1))/3)..."
+            sleep 5
+        done
     fi
     tar -czf "$OUT_DIR/npm/${name}-node_modules.tar.gz" --owner=0 --group=0 -C "$tmp" node_modules
     info "$name: $(du -sh "$tmp/node_modules" | cut -f1) -> $(du -h "$OUT_DIR/npm/${name}-node_modules.tar.gz" | cut -f1) compressed"