Wire up all V1 economy comparison outputs (Phase 2 parity)

[anth-volk]

Context

Phase 2 of the simulation/report V2 migration wires up all the economy-wide comparison outputs that V1 currently returns, so the API can serve complete analysis results. Prior to this work, the economy comparison only computed decile impacts and program statistics.

Changes needed

New database tables

• budget_summary — per-variable fiscal aggregates (household_tax, household_benefits, household_net_income, etc.)
• intra_decile_impacts — 5-category income change distribution per decile (11 rows per report)

Computation wiring (local + Modal, UK + US)

• Poverty rates (overall, by age, by gender, by race) → stored in existing poverty table
• Inequality (Gini, top 10%, top 1%) → stored in existing inequality table
• Budget summary aggregates → stored in new budget_summary table
• Intra-decile income change breakdown → stored in new intra_decile_impacts table

Response structure additions on EconomicImpactResponse

• poverty — list of poverty records (overall + demographic breakdowns)
• inequality — list of inequality records
• budget_summary — list of budget summary records
• intra_decile — list of intra-decile impact records
• detailed_budget — V1-compatible per-program breakdown dict

Other

• Expand UK local program list from 4 to 10 programs (matching Modal)
• Intra-decile helper with two formula variants (V1 original + corrected) and strategy selector

Target branch

app-v2-migration