Focus dashboard on 2024 Census SPM comparison

[MaxGhenis]

What changed

• Makes the first dashboard section a 2024 Census SPM comparison instead of starting with the year selector.
• Adds a current ECPS input-gap table for pension income, housing subsidy, and energy assistance.
• Moves the year selector, recompute controls, baseline card, and state table into a separate "Explore other years" section.
• Keeps sub-dollar diagnostic means visible, so current ECPS pension income shows as $0.20 rather than rounding to $0.

Why

The 2024 Census report comparison is the current focus. Pension and housing subsidy were technically present in diagnostics, but pension was rounded down and housing subsidy was buried in the SPM resource reconstruction table.

Validation

• uv run pytest
• npm run typecheck
• npm run build
• Verified locally in the in-app browser at http://127.0.0.1:3010/