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

docs/build-desktop-packages.md

@@ -0,0 +1,91 @@
+# Desktop packaging (Linux, Arch, Windows)
+
+How to produce distributable desktop packages for JellyTau. All three flows can
+run in Docker so no host toolchain setup is required. Outputs land in `./dist`.
+
+## One builder image (shared with CI)
+
+The deb/rpm and Windows-cross flows build on the **unified registry builder**
+([../Dockerfile.builder](../Dockerfile.builder) →
+`gitea.tourolle.paris/dtourolle/jellytau-builder`), the same image CI uses. It
+carries every packaging tool: Android SDK/NDK, `rpm`/`file` (Linux bundler),
+`cargo-xwin` + `lld` + `llvm` + `nsis` + the `x86_64-pc-windows-msvc` rust target
+(Windows). There is **one** dependency source of truth — no per-stage tool
+installs.
+
+The desktop stages in [../Dockerfile](../Dockerfile) are thin `FROM
+${BUILDER_IMAGE}` environments; the actual build runs at container-run time on
+your bind-mounted source (like the `dev` service), so source edits need no image
+rebuild.
+
+**If you changed `Dockerfile.builder`** (e.g. added a tool), rebuild and push it
+first, or the packaging flows use the stale registry image:
+
+```bash
+scripts/build-builder-image.sh           # build + push :latest to the registry
+# ...or iterate locally without pushing:
+docker build -f Dockerfile.builder -t jellytau-builder:latest .
+BUILDER_IMAGE=jellytau-builder:latest bun run docker:build:windows
+```
+
+Arch uses a separate `archlinux` image ([../Dockerfile.arch](../Dockerfile.arch))
+because `makepkg` is Arch-specific — it is not part of the unified builder.
+
+| Target | Format | Docker command | Functional? |
+|--------|--------|----------------|-------------|
+| Debian/Ubuntu, Fedora | `.deb`, `.rpm` | `bun run docker:build:linux` | ✅ yes |
+| Arch Linux | `.pkg.tar.zst` | `bun run docker:build:arch` | ✅ yes |
+| Windows | NSIS installer + `.exe` | `bun run docker:build:windows` | ✅ yes (unsigned) |
+
+## Linux: deb + rpm
+
+Tauri's bundler produces these natively. The build runs on the existing Ubuntu
+builder image ([../Dockerfile](../Dockerfile), `desktop-linux-build` stage):
+
+```bash
+bun run docker:build:linux            # deb + rpm -> ./dist
+# or, on a host with the Tauri Linux deps installed:
+BUNDLES="deb,rpm" scripts/build-desktop-linux.sh
+```
+
+Runtime dependency: the app links libmpv (audio) and WebKitGTK (webview + HTML5
+transcoded video). The deb/rpm declare these.
+
+> Note: `appimage` is also a valid Tauri target if you want a portable bundle —
+> add it to `BUNDLES`.
+
+## Arch Linux: pacman package
+
+**Tauri has no `pacman` bundle target** (as of tauri-cli 2.9.x — valid targets
+are deb/rpm/appimage/msi/nsis/app/dmg). So we ship a hand-written PKGBUILD in
+[../packaging/arch/PKGBUILD](../packaging/arch/PKGBUILD) and build it with
+`makepkg` on an Arch base image ([../Dockerfile.arch](../Dockerfile.arch)):
+
+```bash
+bun run docker:build:arch             # .pkg.tar.zst -> ./dist
+```
+
+The PKGBUILD is AUR-ready: swap its `source=()` for a release tarball/VCS URL to
+publish. Runtime deps: `webkit2gtk-4.1`, `mpv`, `gtk3`, `libayatana-appindicator`.
+
+`makepkg` refuses to run as root, so the Docker stage builds as a non-root
+`builder` user. Because the image `COPY`s the source at build time, the
+`arch-build` compose service does **not** bind-mount the repo — rebuild the image
+to pick up source changes.
+
+## Windows: NSIS installer cross-compiled from Linux
+
+Produces a working (unsigned) NSIS installer + `.exe` via the official Tauri
+cross-compile path — the `x86_64-pc-windows-msvc` target driven by `cargo-xwin`.
+Video plays via WebView2 and audio via the webview `<audio>` backend. See
+[build-windows.md](build-windows.md) for the full explanation.
+
+```bash
+bun run docker:build:windows                     # NSIS installer + .exe -> ./dist
+WIN_BUNDLES=none bun run docker:build:windows     # exe only, skip bundling
+```
+
+The Docker `windows-cross` stage is a thin layer over the builder, which carries
+`cargo-xwin` + `lld` + `llvm` + `nsis` + the `x86_64-pc-windows-msvc` target.
+Cross-compilation is Tauri's "last resort" path (less tested than building on
+Windows); a `windows-latest` CI job is the fallback if it misbehaves.