Fixes a regression from 0c11cea where local composite actions
(.github/actions/) were referenced with relative paths. When spins
reuse our reusable workflows, GitHub resolves relative action paths
in the context of the calling repo, not infix — breaking the build.
Replace all uses of ./.github/actions/{cache-restore,podman-cleanup}
with kernelkit/actions/{cache-restore,podman-cleanup}@v1 (new repo).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add Raspberry Pi 2B to the bootloader build matrix and raspberrypi-rpi2
to the SD card image builder, enabling full RPi 2B image creation.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
