packaging: macOS app and dmg, Linux tar.gz and AppImage, Windows zip

packaging/macos/package.sh builds FieldCraft.app (io.github.jyviko.fieldcraft, with icon.icns
and the layered Assets.car), signs it with a Developer ID and notarizes it when the
credentials are there and ad-hoc otherwise, and puts it on a drag-to-Applications dmg that
is mounted and checked; fieldcraft-cli goes in its own zip. packaging/linux/package.sh makes
an FHS tar.gz (binaries, .desktop entry, hicolor icons, licences) and an AppImage made with
appimagetool and the type 2 runtime at pinned, hash-checked releases.
packaging/windows/package.ps1 zips fieldcraft.exe and fieldcraft-cli.exe (static CRT,
checked PE headers and icon). Every package carries README.md, LICENSE-MIT, LICENSE-APACHE,
NOTICE and THIRD-PARTY-LICENSES.txt (#72).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

.cargo/config.toml

@@ -1,2 +1,8 @@
 [alias]
 xtask = "run --package xtask --"
+
+# Windows release binaries link the C runtime statically, so they run without the VC++
+# redistributable (packaging/windows/package.ps1 builds with --target, which keeps the flag
+# off build scripts and proc-macros).
+[target.x86_64-pc-windows-msvc]
+rustflags = ["-C", "target-feature=+crt-static"]