feat(build): cross-platform desktop packaging; bump to 0.1.0

Adds Docker-based packaging for Linux desktop (deb/rpm), Arch
(.pkg.tar.zst via makepkg), and Windows. Windows cross-compiles from
Linux via the official Tauri path — the x86_64-pc-windows-msvc target
driven by cargo-xwin — and produces an NSIS installer (nsis via
tauri.conf.json targets, since the CLI rejects --bundles nsis on a Linux
host). Verified end to end: builds jellytau.exe + jellytau_x64-setup.exe.

Unifies everything on one registry builder image (Dockerfile.builder):
Android SDK/NDK, rpm/file, clang(+clang-cl)/lld/llvm/nsis, cargo-xwin and
the msvc target. Packaging tools sit in a trailing layer so tool changes
rebuild in ~1min instead of ~15. Desktop stages are thin FROM
${BUILDER_IMAGE} layers; Arch uses a separate archlinux image.

CLAUDE.md: CI must install no system toolchains — everything lives in the
image. Bumps version 0.0.18 -> 0.1.0 (Windows support + webview audio +
equalizer).

TRACES: UR-003, UR-005 | DR-004

packaging/arch/PKGBUILD

@@ -0,0 +1,52 @@
+# Maintainer: Duncan Tourolle <duncan@tourolle.paris>
+#
+# JellyTau — a cross-platform Jellyfin client (Tauri + SvelteKit).
+#
+# This PKGBUILD builds from the local source tree by default (see the `dev`
+# convenience below), which is what scripts/build-arch.sh uses inside the Arch
+# Docker stage. For AUR distribution, replace the `source=()` line with a release
+# tarball/VCS URL and drop the local-copy prepare() step.
+
+pkgname=jellytau
+pkgver=0.0.18
+pkgrel=1
+pkgdesc="A cross-platform Jellyfin client"
+arch=('x86_64')
+url="https://gitea.tourolle.paris/dtourolle/jellytau"
+license=('MIT')
+# Runtime: libmpv for audio, webkit2gtk for the webview + HTML5 transcoded video.
+depends=('webkit2gtk-4.1' 'mpv' 'gtk3' 'libayatana-appindicator')
+makedepends=('rust' 'cargo' 'bun' 'nodejs' 'pkgconf' 'libsoup3')
+options=('!strip' '!lto')
+
+# Populated from the working tree by scripts/build-arch.sh (SRC env var).
+_srcdir="${JELLYTAU_SRC:-$startdir/../..}"
+
+build() {
+  cd "$_srcdir"
+  export CARGO_HOME="${CARGO_HOME:-$srcdir/cargo-home}"
+  bun install --frozen-lockfile || bun install
+  bun run build
+  # Only the raw binary is needed; packaging is done in package() below so we
+  # control the Arch filesystem layout ourselves rather than via tauri-bundler.
+  (cd src-tauri && cargo build --release --locked)
+}
+
+package() {
+  cd "$_srcdir"
+
+  install -Dm755 "src-tauri/target/release/jellytau" \
+    "$pkgdir/usr/bin/jellytau"
+
+  # Desktop entry
+  install -Dm644 "packaging/arch/jellytau.desktop" \
+    "$pkgdir/usr/share/applications/jellytau.desktop"
+
+  # Icons (hicolor)
+  install -Dm644 "src-tauri/icons/32x32.png" \
+    "$pkgdir/usr/share/icons/hicolor/32x32/apps/jellytau.png"
+  install -Dm644 "src-tauri/icons/128x128.png" \
+    "$pkgdir/usr/share/icons/hicolor/128x128/apps/jellytau.png"
+  install -Dm644 "src-tauri/icons/128x128@2x.png" \
+    "$pkgdir/usr/share/icons/hicolor/256x256/apps/jellytau.png"
+}

packaging/arch/jellytau.desktop

@@ -0,0 +1,9 @@
+[Desktop Entry]
+Type=Application
+Name=JellyTau
+Comment=A cross-platform Jellyfin client
+Exec=jellytau
+Icon=jellytau
+Terminal=false
+Categories=AudioVideo;Player;Audio;Video;
+StartupWMClass=jellytau