Add system prove-proxy endpoints to network configuration

[hellojason3]

Summary

• Add system_prove_proxy_url to all three network configurations.
• Keep prove_proxy_url unchanged for user-facing proving requests.
• Preserve the latest multi_chain Genesis contracts, ABI files, token artifacts, and compiler provenance unchanged.

Head commit: dd9f3384e2b0be8621036c58a3b36248d3138404.
The net diff against multi_chain is one file, nine added lines in config.json.

Related Change

Companion configuration for PsyProtocol/psy-node#10.
The node PR already pins this remotely published Genesis commit, resolving its submodule conflict while retaining the role-split configuration.

Endpoint Behavior

The new system endpoint defaults to the existing prove-proxy URL in each network. These defaults support an all-role proxy; they do not provision or route two separate processes.

Deployments that split user and system roles must override the system endpoint to reach the actual system-role process. A user-only endpoint is not a valid relayer system endpoint; the companion node change checks the reported role.

This PR does not deploy services, change live routing, regenerate contracts, or alter Genesis balances. The separate local Genesis regeneration audit and its artifact differences are not included.

Validation

Validated with the companion node merge against multi_chain at 5b7f4e1e11adf4607a958bc39e863a2a80b5a7a6:

• cargo test --release --locked -p psy_config --lib: 6 passed.
• cargo test --release --locked -p psy_prover --test prove_proxy_role: 5 passed.
• Relayer release tests filtered by system_prove_proxy: 5 passed, covering required configuration, blank entries, system-role acceptance, user-role rejection, and closed-port failure.
• Relayer user_pool_url_is_not_a_fallback: 1 passed.
• Compared the Genesis tree to multi_chain: only config.json differs; generated artifact hashes and sizes were verified.
• Fresh remote clone of the companion node branch successfully initialized every recursive submodule, including this exact Genesis commit.
• Whitespace checks and independent merge review passed.

No live deployment or transaction E2E was performed for this configuration PR.