Prysm v7.1.6 Adds SSZ Proofs, Doubles RPC Rate Limits

Prysm v7.1.6 released plus Gloas (ePBS) work, PeerDAS data-column support, and SSZ-QL proofs. Adds --postpone-shutdown-for-proposals flag, builder API SSZ default, and doubled RPC rate limits (10 req/s). Gossip validation covers execution payload envelopes. Operators urged to update.