bread-ecosystem's ci/build.sh used to derive the image tag and cache
volume name from basename(repo_root) — but every product's CI checks
out into a directory literally named "src", so in real CI runs this
resolved to "bread-ci:src" for every product, not "bread-ci:breadpad".
Harmless while breadpad was the only consumer; would have silently
collided (shared image tag, shared cargo-target cache) the moment a
second product started using it. Fixed upstream, bumping the pin here
to pick it up and passing "breadpad" explicitly.
Moves the Containerfile and build.sh added in the previous CI fix up
into bread-ecosystem/ci/, so other GTK4 layer-shell products in the
ecosystem can share it instead of each carrying their own copy. This
repo's ci/build.sh is now a thin wrapper that clones bread-ecosystem
at the commit pinned in ci/bread-ecosystem.rev and delegates to its
ci/build.sh — pinned by sha rather than tracking main, so an unrelated
change over there can't silently break this repo's release builds
(the failure mode the bread-theme test fix a moment ago was caused by).
Verified locally: clippy, test, and release build all pass through
the new delegator path.
