Moves normHeader/resolveColumn/parseDate/toNumber out of fuel-import-parse
into a new src/lib/import-parse.ts so plant-hours can reuse them. Adds
parseTime (HH:MM, 24h, single-digit hour normalised). Adds the
PLANT_COL_ALIASES table for the plant-hours route. fuel-import-parse
becomes a thin re-export shim — the fuel-logs route and its existing
test file are unchanged.
