Point decay and zero-sum DKP

[avandenberghe]

Summary

Implement point decay and zero-sum DKP distribution — two common DKP variants that prevent point hoarding and encourage spending.

Point decay

Periodically reduce all member balances by a percentage to prevent indefinite point hoarding.

• Configurable decay rate (%) and frequency (days/weeks)
• Decay applies to earned and adjustment balances
• Each decay run creates decay transactions in the ledger (Database schema: transaction-based points ledger #3)
• Manual trigger from ACP + optional cron job
• Decay sync: recalculate all decay in one pass

Zero-sum DKP

When loot is distributed, the DKP spent by the buyer is redistributed equally among all raid attendees who did NOT receive loot.

• On item purchase, calculate item_value / (attendees - buyers) and credit each non-buyer
• Zero-sum bonus transactions with account = 'zerosum'
• Zero-sum sync: recalculate all zero-sum bonuses retroactively
• Toggle per pool: not all pools need zero-sum

Configuration

• Per-pool settings: decay enabled, decay rate, decay frequency, zero-sum enabled
• Global toggle to enable/disable decay system-wide

Reference

• Old bbDKP: decay sync, zerosum sync log types
• EQdkp Plus: core/auto_point_adjustments.class.php
• Archived language keys: RAIDDECAY, ADJDECAY, DECAY, ZSVALUE, ZEROSUM in bbguild/contrib/archive/language/*/dkp_common.php