v0.1.0

Add build:linux task producing a Linux AppImage, served at /app.AppImage

`deno task build:linux` mirrors build:mac: it builds the Fresh app, cross-
compiles the kiosk launcher (scripts/launch-linux.ts) for x86_64 Linux, then
packages it into dist/cmg-x86_64.AppImage via scripts/build-appimage.ts, which
downloads appimagetool and runs it with APPIMAGE_EXTRACT_AND_RUN=1 (no FUSE or
squashfs-tools required on the host).

AppImage packaging is Linux-only, so .github/workflows/build-appimage.yml builds
it on a Linux runner and publishes it to GitHub Releases on tag push. The deploy
serves it at /app.AppImage by redirecting (302) to the latest release asset. The
redirect is built with a plain Response, not Response.redirect(), so the global
CORS middleware can still set its header (Response.redirect headers are
immutable, which otherwise 500s).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>