Install the Cloud SQL migration and household mirror-event workflows from uv.lock #4079

Two operational database workflows still install the Public API's dependencies with an unlocked pip install -e ".[dev]", and run their Python scripts with the bare python that actions/setup-python provides:

• .github/workflows/migrate-v1-cloud-sql.yml (job migrate), which runs .github/scripts/migrate_v1_cloud_sql.sh against the staging and production v1 Cloud SQL databases, and is called by push.yml before each staging and production deployment;
• .github/workflows/process-v1-household-mirror-event.yml (job process-event), which runs .github/scripts/run_household_mirror_event_operator.sh to copy one retained v1 household create-event to the v2 database.

#3997 registered both installs as exceptions to api.dependencies.install-from-lock, to be removed when "the job installs with uv sync --frozen and runs its scripts through uv run --frozen, after a run against the staging database succeeds".

Done when

• Both jobs set up uv with astral-sh/setup-uv at the version the Cloud Run image and the release job use (0.13.4), set UV_PYTHON to 3.12, and install with uv sync --frozen.
• Both scripts run their Python commands through uv run --frozen, with every environment variable the commands read still reaching them.
• Both exceptions are removed from rules/registry.toml, and the locked-installs quality guard passes.
• Tests cover the scripts' locked invocations and the jobs' locked installs.
• A manually dispatched staging run of each workflow from the pull request branch succeeds before the pull request merges.