Select UK local-authority lookup by dataset

[anth-volk]

Fixes #541

Adds typed bundle metadata for the LAD22 and LAD23 lookup assets. Explicitly listed legacy UK dataset identities resolve to LAD22; every other identity defaults to LAD23. Managed lookup files are verified against pinned SHA-256 hashes before use, while an explicit caller-owned path remains an intentional override.

The local-authority output accepts the managed dataset identity so service callers can select metadata that matches the codes emitted by the dataset.

Test plan:

• make format
• make lint
• uv run --python 3.13 --extra dev pytest tests/test_uk_geography_assets.py tests/test_local_authority_impact.py tests/test_uk_regions.py tests/test_bundle.py tests/test_bundle_metadata.py -q
• uv run --python 3.13 --extra dev python scripts/bundle.py check

[anth-volk]

Superseded by PolicyEngine/policyengine-sim-api#705. The replacement identifies the authority roster from actual la_code_oa values and does not route lookup data by dataset name or release identity, so no PolicyEngine.py change is required.

[anth-volk]

Update: the replacement simulation API work is now PolicyEngine/policyengine-sim-api#706. GitHub closed #705 when its branch was renamed.