Add diaspora remittance inflow

[speedcom]

Summary

• Per-capita diaspora inflow channel calibrated to NBP BoP 2024 (~18 mld PLN/year, ~40 PLN/person/month)
• ER pass-through (50%), secular trend (2%/year), counter-cyclical sensitivity to excess unemployment
• Completes secondary income picture: secondaryIncome = euFunds - remittanceOutflow + diasporaInflow
• SFC Identity 2 (deposits) and Identity 4 (NFA/BoP) updated; no new identity needed

Changes

File	Change
SimConfig.scala	+5 env vars (REMITTANCE_ENABLED/PER_CAPITA/ER_ELASTICITY/GROWTH_RATE/CYCLICAL_SENS)
OpenEconomy.scala	+diasporaInflow parameter; secondaryIncome formula updated
World.scala	+diasporaRemittanceInflow field
SfcCheck.scala	+diasporaInflow in MonthlyFlows; Identity 2 formula + Identity 4 comment
Simulation.scala	Compute inflow; pass to OpenEconomy; single-bank + multi-bank deposits; SFC flows; World
Main.scala	nCols 188→190; +2 output columns (DiasporaRemittanceInflow, NetRemittances); CSV header + colNames
DiasporaRemittanceSpec.scala	NEW — 20 tests
IntegrationSpec.scala	188→190
IntegrationFullSpec.scala	188→190

Test plan

• sbt test — 1166 passed, 0 failed
• REMITTANCE_ENABLED=true OPEN_ECON=true — DiasporaInflow > 0, no SFC FAIL
• REMITTANCE_ENABLED=true IMMIG_ENABLED=true — NetRemittances = inflow − outflow, no SFC FAIL
• REMITTANCE_ENABLED=false — DiasporaInflow = 0, NetRemittances = 0
• BDP=0 smoke test — no SFC FAIL