v0.3.0-rc7 — Raspberry Pi (homy) deploy + aarch64 CI build

- fix(midi): dispatch CC mappings via the World-resource registry, so
  PyO3/REPL-registered CC bindings (incl. Grid fader -> executor blend)
  actually dispatch on the daemon (+ regression tests)
- feat(projects): homy project; rightmost Intech Grid fader (CC 39) ->
  warm_white executor blend; headless systemd unit (dashboard control surface)
- ci(aarch64): Docker cross-build for Raspberry Pi as a GitLab pipeline job
  (orb-daemon-aarch64.tar.gz: binary + libpython3.13 + matching stdlib + dist)
- chore(deploy): pin flake-cross.nix to flake.lock revs