Add tourism: inbound/outbound services trade

[speedcom]

Summary

• Inbound tourism (~5% GDP, GUS TSA 2023) and outbound tourism (~3% GDP, NBP BoP 2023) as direct deposit flows routed through OpenEconomy into BoP
• Seasonal fluctuations (peak July, ±40% amplitude), ER sensitivity (elasticity 0.6), secular growth (3%/year), COVID-type demand shock capability
• 10 env vars (TOURISM_ENABLED, _INBOUND_SHARE, _OUTBOUND_SHARE, _ER_ELASTICITY, _SEASONALITY, _PEAK_MONTH, _GROWTH_RATE, _SHOCK_MONTH, _SHOCK_SIZE, _SHOCK_RECOVERY)
• 4 output columns (190–193): TourismExport, TourismImport, NetTourismBalance, TourismSeasonalFactor
• SFC Identity 2 (bank deposits) + Identity 4 (NFA via tradeBalance) updated
• Bonus: importedInterm.sum → kahanSum in OpenEconomy for FP precision
• 1192 tests pass (26 new in TourismSpec)

Test plan

• sbt "testOnly *TourismSpec" — 26/26 green
• sbt test — 1192/1192 green (0 failures)
• TOURISM_ENABLED=true OPEN_ECON=true FIRM_SIZE_DIST=gus sbt "run 2000 30 test_tourism pln" — no SFC FAIL, columns 190–193 non-zero, seasonal oscillates 0.6–1.4