P2E: add admin reward console

[ilyar]

Source PRD: tasks/prd-full-play-to-earn.md
Parent epic: #86
PRD section: US-011

Description

Operators need to manage pools, campaigns, claims, abuse review, and payout recovery without direct database edits.

Acceptance Criteria

• Admin UI has tabs for Reward Pools, Campaigns, Claims, Payouts, Abuse Review, and Audit.
• Admin can create draft pools/campaigns and preview impact before activation.
• Admin can approve, hold, reject, or cancel claims with required reason.
• Admin can retry failed payouts through backend-only provider APIs.
• Admin actions write immutable audit events.
• Non-admin users cannot load reward admin data.
• Verify in browser using Playwright.

Constraints

• Keep current paid PvP settlement as entry fee, not player-funded prize pool.
• Do not make Season Points redeemable or refundable.
• Keep payout/compliance/provider secrets backend-only.
• Treat this as deferred future-phase work until mechanics/self-host production readiness is stable.

Notes

Reuse admin auth principles from the existing admin dashboard PRD, but keep reward operations separated from balance corrections.