fix(ci): include acceptance scripts in backend checks

Supply repository scripts as a named build context for the backend check stage so containerized regression tests can import the same acceptance helpers as local tests. Keep operator scripts out of the runtime image.

deploy/Dockerfile.backend

@@ -10,6 +10,7 @@ COPY . .
 RUN uv sync --locked --no-dev
 
 FROM base AS check
+COPY --from=project-scripts . /scripts/
 RUN uv sync --locked && uv run pytest && uvx ruff==0.14.14 check --select F,E9,B src tests
 
 FROM base AS browser-download

scripts/ci.py

@@ -216,7 +216,8 @@ def check():
     save(ROOT / 'build.json', build)
     for part in IMAGES:
         print('Checking ' + part, flush=True)
-        run('docker', 'build', '--provenance=false', '--platform', 'linux/amd64', '--target', 'check',
+        contexts = ['--build-context', f'project-scripts={ROOT / "scripts"}'] if part == 'backend' else []
+        run('docker', 'build', *contexts, '--provenance=false', '--platform', 'linux/amd64', '--target', 'check',
             '-f', ROOT / f'deploy/Dockerfile.{part}', ROOT / part)
         reused = existing_image(part, build)
         local = reused or 'alphapulse-ci:' + label + '-' + part