Upgrade Besu 26.7.1 Now to Patch Security Flaws

Besu 26.7.1 patches security vulnerabilities — upgrade now. New caps: --rpc-max-active-filters (default 1000), --rpc-filter-timeout-seconds (120), --rpc-ws-max-active-subscriptions (100,000). Deprecates --min-block-occupancy-ratio; renames BFT option to emptyblockperiodseconds. Fixes engine_newPayload invalid payload error, integer overflow, and txpool zero-cost rejection.