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

Dockerfile

@@ -1,4 +1,11 @@
 # Multi-stage build for JellyTau - Tauri Jellyfin client
+#
+# The desktop packaging stages (desktop-linux-build, windows-cross) build FROM
+# the unified registry builder image, which carries every packaging tool. Declared
+# here (before the first FROM) so it's in scope for those stages' FROM lines.
+# Override for local iteration: --build-arg BUILDER_IMAGE=jellytau-builder:latest
+ARG BUILDER_IMAGE=gitea.tourolle.paris/dtourolle/jellytau-builder:latest
+
 FROM ubuntu:24.04 AS builder
 
 ENV DEBIAN_FRONTEND=noninteractive \
@@ -108,6 +115,30 @@ RUN cd src-tauri && cargo fetch && cd .. && \
     bun run tauri android build --apk true && \
     echo "APK build complete!"
 
+# Desktop packaging stages build FROM the unified registry builder image (see the
+# BUILDER_IMAGE ARG at the top), which already carries every packaging tool
+# (rpm/file for Linux, mingw-w64 + nsis + the x86_64-pc-windows-gnu rust target
+# for Windows). ONE source of dependency truth, shared with CI — no per-stage
+# apt/rustup here.
+
+# Linux desktop packaging environment (deb + rpm; Arch is Dockerfile.arch).
+# Thin layer over the builder — the actual build runs at container-run time on
+# the bind-mounted source (see docker-compose.yml / scripts/build-desktop-linux.sh),
+# matching the `dev` service model. Run standalone with:
+#   docker run --rm -v "$PWD:/app" -v "$PWD/dist:/app/dist" <img> \
+#     bash -c "OUTPUT_DIR=/app/dist scripts/build-desktop-linux.sh"
+FROM ${BUILDER_IMAGE} AS desktop-linux-build
+WORKDIR /app
+CMD ["bash", "-c", "OUTPUT_DIR=/app/dist scripts/build-desktop-linux.sh"]
+
+# Windows cross-compile environment (MSVC target via cargo-xwin). Video works via
+# WebView2 and audio via the webview <audio> backend; NSIS installer is produced
+# from Linux by cargo-xwin. Default bundles NSIS; override WIN_BUNDLES=none for
+# exe-only. Build runs at container-run time like above.
+FROM ${BUILDER_IMAGE} AS windows-cross
+WORKDIR /app
+CMD ["bash", "-c", "OUTPUT_DIR=/app/dist WIN_BUNDLES=${WIN_BUNDLES:-nsis} scripts/build-windows-cross.sh"]
+
 # Final output stage
 FROM ubuntu:24.04 AS final
 RUN apt-get update && apt-get install -y --no-install-recommends \