Add tax-exempt interest and charitable deduction targets

[MaxGhenis]

Summary

• re-enable national SOI tax-exempt interest aggregate targets
• add national AGI-bin tax-exempt interest dollar and filer-count targets to the ETL and target config
• add national SOI charitable deduction aggregate/count targets
• update target-config and ETL coverage tests

Context

The remaining outlier scan showed a few non-mortgage, non-LTCG variables that were still targetable. The locally available H5 has tax_exempt_interest_income at about $82.6B for 2024 with a max record around $244M; the stored 2023 SOI exempt-interest aggregate is $66.1B. It also has charitable_deduction at about $301.1B; the stored 2023 SOI charitable-contribution deduction aggregate is $212.0B.

These are much less severe than mortgage interest or the prior capital-gains issue, but both are targetable with existing SOI rows. This follows the same logic as #868: a high-error soft target is preferable to leaving the aggregate unconstrained when the variable can affect downstream federal/state tax calculations.

Validation

• uv run pytest tests/unit/calibration/test_target_config.py -q
• uv run pytest tests/unit/calibration/test_target_config.py tests/unit/test_etl_irs_soi_overlay.py::test_load_national_geography_ctc_agi_targets_creates_capital_income_domains tests/unit/test_etl_irs_soi_overlay.py::test_workbook_domain_targets_include_charitable_deduction -q
• uv run ruff format --check policyengine_us_data/db/etl_irs_soi.py tests/unit/test_etl_irs_soi_overlay.py tests/unit/calibration/test_target_config.py
• uv run ruff check policyengine_us_data/db/etl_irs_soi.py tests/unit/test_etl_irs_soi_overlay.py tests/unit/calibration/test_target_config.py