Contracts: WarBow PvP on DOUB + WarBow-epoch score reset

Context

WarBow PvP with DOUB costs and independent WarBow epoch reset. Parent epic: #238 (closed).

Relevant files

• contracts/src/TimeCurve.sol WarBow section → TimeArena.sol
• Tests: TimeCurveWarBow*.t.sol

Acceptance criteria

• Steal 1000 DOUB, Guard 10000 DOUB, steal-limit override 50000 DOUB, Revenge 1000 DOUB
• All WarBow spends route through DOUB accounting (no CL8Y)
• BP/scoring rules retained from docs/product/primitives.md unless spec amends
• On WarBow timer epoch roll: reset live BP/podium scores; persist epoch id for admin finalizeWarbowPodium(epoch, first, second, third)
• Flag plant/claim mechanics retained (claim cost = 0 DOUB)

Verification checklist

• Forge: steal/guard/override pull DOUB amounts
• Epoch reset clears battlePoints but finalizeWarbowPodium(oldEpoch, ...) still pays from that epoch's pool