Fix Michigan homestead property tax credit income limit

[MaxGhenis]

Fixes #8241.

Summary

• add the MI-1040CR household resources eligibility limit for the Michigan homestead property tax credit
• apply the limit in mi_homestead_property_tax_credit_eligible so above-limit senior renter cases do not receive the alternate credit
• add 2024/2025 boundary tests and a 2025 integration reproduction case

Tests

• uv run python -m policyengine_core.scripts.policyengine_command test policyengine_us/tests/policy/baseline/gov/states/mi/tax/income/credits/homestead_property_tax -c policyengine_us
• uv run pytest policyengine_us/tests/test_parameter_files.py policyengine_us/tests/test_system_import.py -q
• uv run ruff check policyengine_us/variables/gov/states/mi/tax/income/credits/homestead_property_tax/mi_homestead_property_tax_credit_eligible.py

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (92fdab8) to head (034952e).
⚠️ Report is 77 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #8424   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         1    -1     
  Lines           57        13   -44     
  Branches         1         0    -1     
=========================================
- Hits            57        13   -44     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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