Add congressional district vintage crosswalk support

[MaxGhenis]

Summary

• translate old-vintage SOI congressional district Ledger facts onto the current 118th-congress CD surface via a proportional crosswalk
• thread the crosswalk through fiscal target compilation, support assignment, release builds, and read-only scoring
• require support H5 provenance attrs to match the crosswalk before compiling crosswalk-translated CD targets
• update CD target profile expectations to the current 436-district surface and add parser/translation/provenance tests

Closes #205.

Verification

• uv run --python 3.13 ruff check packages/populace-build/src/populace/build/us_runtime/congressional_district_vintage.py packages/populace-build/src/populace/build/us_runtime/__init__.py tools/build_us_puf_support_base.py tools/build_us_fiscal_refresh_release.py tools/score_us_fiscal_targets.py packages/populace-build/tests/test_us_congressional_district_vintage.py packages/populace-build/tests/test_us_fiscal_refresh_builder.py packages/populace-build/tests/test_us_puf_support_base_builder.py
• uv run --python 3.13 --package populace-build --group dev python -m pytest packages/populace-build/tests/test_us_congressional_district_vintage.py packages/populace-build/tests/test_us_congressional_district_geography.py packages/populace-build/tests/test_us_fiscal_targets.py packages/populace-build/tests/test_us_fiscal_refresh_builder.py packages/populace-build/tests/test_us_puf_support_base_builder.py -q
• git diff --cached --check before commit / git diff --check after edits
• read-only review cycle: first pass found support-provenance and validation issues; second pass found stale attr-stamping without assignment; final pass reported no actionable findings