Package the desktop app for Arch, Debian and Windows

electron-builder produces j621-desktop_*_amd64.deb,
j621-desktop-*.pkg.tar.zst (zstd, lean Arch dependencies instead of the
Electron 2 era default set) and a per-user NSIS installer cross-built with
wine. The launcher entry and Electron's desktopName now agree on
io.j621.desktop so window association works, and package metadata points
at the repository homepage and the non-commercial licence.

desktop/electron-builder.yml

@@ -29,6 +29,27 @@ linux:
     desktop build talks to a J621 backend over the network, the same way the
     web app does.
   icon: build/icon.png
+  syncDesktopName: true
+
+pacman:
+  compression: zstd
+  artifactName: ${name}-${version}.pkg.tar.zst
+  # Electron's shared-library requirements on Arch (the electron-builder
+  # defaults still list an ancient Electron 2 dependency set).
+  depends:
+    - gtk3
+    - nss
+    - libxss
+    - libxtst
+    - xdg-utils
+    - at-spi2-core
+    - libsecret
+    - libnotify
+    - alsa-lib
+    - libcups
+    - libdrm
+    - mesa
+    - libxkbcommon
 
 win:
   target: