Bounty system revamp

Bounties used to pay flat. That created a meta where players would farm alts to drain treasuries. New formula:

• Base payout still set by the bounty placer
• Multiplied by min(1.0, target.kd_last_7d / 1.5)
• Capped at 2× the placed amount

What this means in practice: bounties on actually-dangerous players pay full freight. Bounties on alts pay pennies.

Other tweaks

• Bounty kill notifications now show in #larp-relay
• Killer's faction gets a 10% bonus when they're at war with the target's faction