v1.9

Changes

• Fixed mass and fuel calculation inconsistency in to_trajectory() method
  • Corrected dt calculation: ts_final / (n - 1) instead of ts_final / n
  • DataFrame now uses optimizer's mass values directly instead of recalculating
  • This fixes ~5% fuel underestimation bug
• Added temperature shift (dT) support for non-ISA conditions
• Code cleanup and import improvements
• Made autoscale_cost optional parameter

Full Changelog: v1.8...v1.9