Whiteboard and tasks-source save/clear used to just tell the user to reload the page to see the change. Both endpoints always assign a successful "set" to the calling user, so the new state is fully known client-side already -- rewrite the "Currently using/showing ..." block in place instead, no server round trip or reload needed. Also adds .gitea/workflows/firmware-build-check.yml: builds both board variants (devkit, xiao) on every push touching firmware/**, unlike firmware-release-build.yml which only builds on a version.txt bump. Verified both builds succeed locally against the actual ESP-IDF toolchain before wiring this in.