Function compute_timeline 

pub fn compute_timeline(
    name: &str,
    initial_total_kg: f64,
    initial_dry_kg: f64,
    events: &[MassEvent],
) -> MassTimeline

Generate a mass timeline from an initial state and ordered events.

For each event:

• FuelBurn: applies Tsiolkovsky equation, reduces propellant
• ContainerJettison: reduces dry mass
• DamageEvent: reduces dry mass (structural loss)
• Resupply: adds to propellant (or dry mass depending on context)

Returns a MassTimeline with snapshots before and after each event.