CI: adopt the shared pinned-Arch-container build system

Adds ci/build.sh + ci/bread-ecosystem.rev (pinned to bread-ecosystem
147cfbbf96ae4b171027defa1130d2caddb934b1), points the three release
workflows' build step through it, and adds check.yml as breadarr's first
lint/test gate on feature/fix branches. No ci/deps.txt: verified ort-sys's
build.rs has no system build-time requirements beyond rust/base-devel
(its download-binaries feature is pure-Rust ureq/lzma-rust2/hmac-sha256).

ci/build.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Delegates to bread-ecosystem's shared CI build image/script, pinned to
+# the commit in ci/bread-ecosystem.rev — not `main`. bread-ecosystem's CI
+# files now affect every product's release pipeline, so bumping the pin
+# is a deliberate act instead of silent drift (see the bread-theme test
+# that broke here for exactly that reason, before it was pinned by rev).
+#
+# Usage: ci/build.sh cargo build --release --locked
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+REV="$(cat "${ROOT}/ci/bread-ecosystem.rev")"
+
+CACHE_DIR="/tmp/bread-ecosystem-ci-${REV}"
+if [ ! -d "$CACHE_DIR" ]; then
+    rm -rf /tmp/bread-ecosystem-ci-*
+    git clone https://git.breadway.dev/Breadway/bread-ecosystem.git "$CACHE_DIR"
+    git -C "$CACHE_DIR" checkout --quiet "$REV"
+fi
+
+bash "${CACHE_DIR}/ci/build.sh" breadarr "$ROOT" "$@"