ci: build on bread-ecosystem's shared Arch container

Route dev/beta/release build steps through ci/build.sh, pinned to
bread-ecosystem@147cfbb, instead of installing toolchain/libraries
directly on the bare runner. Adds ci/deps.txt for the build-time-only
packages breadcast needs beyond the shared image's base set (jsoncpp
and libcrypto for breadcast-caststream-sys's build.rs; gstreamer and
gst-plugins-base-libs for the gstreamer-app/-video sys crates) --
deliberately excludes bakery.toml's runtime-only plugin deps
(pipewire/bad/hlssink3/va), which are loaded dynamically by name and
never linked at compile time. Also adds check.yml to run clippy/test
on feature/fix branches ahead of a release build, matching breadpad's
already-migrated pattern.

.forgejo/workflows/check.yml

@@ -0,0 +1,24 @@
+name: check
+
+# Fast-fail lint/test on short-lived work branches, before it ever reaches
+# main and triggers a dev-track release build.
+on:
+  push:
+    branches: ['feature/**', 'fix/**']
+
+jobs:
+  check:
+    runs-on: [self-hosted, hestia]
+    steps:
+      - name: checkout
+        run: |
+          set -euo pipefail
+          rm -rf src && mkdir src
+          git clone --branch "${GITHUB_REF_NAME}" --depth 1 \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" src
+
+      - name: clippy
+        run: cd src && bash ci/build.sh cargo clippy --workspace --all-targets --locked -- -D warnings
+
+      - name: test
+        run: cd src && bash ci/build.sh cargo test --workspace --locked