EIA stores fuel types as codes (NG, NUC, WND, SUN, COL, WAT) but
the chart expected display names (gas, nuclear, wind, solar, coal,
hydro). All data was falling through to "other". Added EIA_FUEL_MAP
lookup in pivotGenerationData to resolve codes before categorizing.
Add error.tsx files for all route segments (/, /map, /trends,
/demand, /generation) with retry buttons. Backfill script ran
successfully: ~30K electricity demand records, ~253K generation
mix records, and 233 commodity price records across all 7 regions.
