Regenerate SPI income projection targets from the 2023-24 base

[MaxGhenis]

Problem

PR #390 updates the live HMRC SPI target source to the 2023-24 ODS and maps that actual tax year to calendar 2024, but policyengine_uk_data/storage/incomes_projection.csv remains a checked-in generated artifact from the older SPI projection path. hmrc_spi.py skips projection rows at or before _SPI_YEAR and uses incomes_projection.csv for later years, so 2025+ HMRC income-band targets can still reflect the older base distribution.

Proposed work

Regenerate the projection inputs from the 2023-24 SPI base and commit the resulting incomes_projection.csv after reviewing aggregate totals and high-income-band behavior. If needed, modernize utils/incomes_projection.py so it derives its base targets from the same SPI parser used by targets/sources/hmrc_spi.py rather than the older storage/incomes.csv path.

Context

Found during review of #390. This is separate from the ONS age parsing CI failure fixed there.