Cleanup Bot

[arrivets]

Refer to https://github.com/Arkiv-Network/arkiv-architecture/blob/main/arkiv/tokenomics/arkiv-fee-spec.md

Spec §2: V1 default cleanup is a permissionless bot operated by Golem that
scans for expired entities and calls DELETE_ENTITY, paying the standard fee.

Likely a new service (separate repo), not arkiv-op-reth code. Scope:

• Periodically scan entity expiry index for entities past expiresAt
• Submit DELETE_ENTITY txs at a controlled rate (rate-limit + per-block budget
  on the bot side, not the protocol — the protocol has none by design)
• Wallet management: bot holds GLM, tops up from a Golem treasury account
• Metrics: expired-entities-pending, deletions-per-block, GLM spent, failures

Depends on: permissionless DELETE shipped on-chain.