Remove survey-based national calibration targets

[MaxGhenis]

Summary

• remove circular survey-derived/SPM-preservation targets from dense national calibration: SPM thresholds, capped housing subsidy, capped work-childcare, non-Part-B medical/OTC/premium aggregates, and gross alimony/child-support levels
• keep defensible component anchors for SPM-relevant expenses: ACS 2024 state/national contract rent and owner real-estate taxes, BLS CE 2024 childcare expenses, and IRS SOI itemized real-estate-tax amount/count targets
• add non-gross accounting constraints that alimony paid minus received and child support paid minus received equal zero, with absolute-error scaling so sparse ECPS keeps those zero targets
• keep age-bucketed health calibration limited to Medicare Part B and add regression tests for national loss/ETL target inclusion/exclusion

Tests

• env -u UV_FROZEN uv run pytest tests/unit/calibration/test_loss_targets.py tests/unit/test_etl_national_targets.py tests/unit/datasets/test_enhanced_cps_seeding.py
• git diff --check

[MaxGhenis]

Closing in favor of #831, which uses the same commit from a PolicyEngine/policyengine-us-data branch so required CI can run.