Upgrade FlowShopScheduling from satisfaction to optimization (Value = Min<u64>)

[isPANN]

Motivation

FlowShopScheduling is currently a satisfaction/decision model (Value = Or, with a deadline field). Per the convention established in #765 and the JobShopScheduling rework in #760, scheduling problems should be optimization models that minimize makespan directly.

Requested Change

• Change Value from Or to Min<u64>
• Remove the deadline field
• evaluate() returns Min(Some(makespan)) for valid permutations, Min(None) for invalid configs
• Update CLI --deadline to no longer apply to FlowShopScheduling
• Update paper entry to optimization formulation
• Update canonical example optimal_value from true to the actual makespan
• Update tests accordingly

Reference

See the JobShopScheduling optimization conversion in PR #760 for the exact pattern.