The Docker build target now runs `make clean all` instead of bare
`make`, so it rebuilds regardless of an existing build/sdlamp2.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Uses ubuntu:22.04 arm64 image running under QEMU emulation to produce
aarch64 binaries that match the target device exactly (same glibc, same
distro). Replaces the broken Buildroot cross-compilation approach.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
