echonet: squash timestamp + block metadata changes for editing

[ron-starkware]

Squashes the rebased ron/add-timestamp-to-block stack into a single commit on top of main for ad-hoc editing. Combines:

• echonet: rename replay functions before getting block metadata
• echonet: share json parse func
• echonet: fetch block metadata from echonet
• echonet: Add timestamp to block metadata

[cursor]

PR Summary

Medium Risk
Changes consensus proposal init gas prices/version and FIFO block sequencing (empty blocks); failures fall back to defaults but incorrect replay could affect block validity in Echonet mode.

Overview
This PR extends Echonet replay so block proposals use canonical mainnet metadata (not just a timestamp): timestamps, block numbers, L1/L2 gas prices, and Starknet version flow from mempool → batcher → consensus orchestrator.

API rename: get_batch_timestamp / resolve_batch_timestamp become get_block_metadata / resolve_block_metadata, returning the new ReplayMetadata struct instead of a bare u64.

Mempool (FIFO/Echonet): resolve_metadata now tracks block number (including empty blocks), and in Echonet mode optionally HTTP-fetches echonet/get_block_metadata from the recorder (shared JSON helper with tx metadata). Gateway adds behavior_mode + recorder_url and sets effective Starknet version at startup from echonet. Consensus uses override_block_metadata to apply replayed prices/version in ProposalInit; Cende blobs carry proposal starknet_version instead of hardcoded LATEST. Config schema, node pointers, Grafana panels, and tests are updated accordingly.

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