Pin Fix, Cooldown Policy, Min-Spec Warning

Miner Experience

• Fixed a race condition that could return a 500 when pinning a race selection twice in quick succession.
• Cooldown behavior on rejected submissions is now documented: file-size and validation rejections keep the cooldown, security-analysis rejections shorten it to 2 minutes, and system errors release it.

Validator

• The validator now logs a loud warning at startup when the host is below minimum spec (6 vCPU / 12 GiB RAM), catching under-provisioned machines before they produce near-zero scores.

Frontend

• Landing and leaderboard pages load significantly faster (smaller fonts, inlined critical CSS, deferred chart rendering).