starknet_transaction_prover: redact URL credentials in logs and add startup banner

[avi-starkware]

Adds redact_url_host which collapses a URL to scheme://host[:port],
dropping userinfo, path, and query. The CLI-override logs for
rpc_node_url and blocking_check_url and a new startup banner all
route through it so credentials embedded in those URLs cannot reach a log
sink.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[cursor]

PR Summary

Low Risk
Observability-only changes; runtime proving, RPC, and auth behavior are unchanged.

Overview
Introduces redact_url_host, which logs URLs as scheme://host[:port] only—stripping userinfo, path, query, and fragment—and uses "<invalid url>" on parse failure so raw strings never hit logs.

CLI override messages for rpc_node_url and blocking_check_url now log through this helper instead of full URLs. A new startup info! banner records version, git SHA, chain id, redacted RPC host, fee-validation and blocking-check flags, and OHTTP enablement without sensitive URL parts.

Unit tests cover credentials, default ports, fragments, and invalid input.

^{Reviewed by Cursor Bugbot for commit 948a1e9. Bugbot is set up for automated code reviews on this repo. Configure here.}

[reviewable-StarkWare]

This change is 

[avi-starkware]

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• starknet_transaction_prover: proving-job duration + outcome metrics #14168
• starknet_transaction_prover: Prometheus /metrics endpoint with build_info #14167
• starknet_transaction_prover: global panic hook + graceful SIGTERM shutdown #14166
• starknet_transaction_prover: per-request structured log with request-id #14165
• starknet_transaction_prover: redact URL credentials in logs and add startup banner #14164 👈 (View in Graphite)
• starknet_transaction_prover: add /health endpoint via HealthLayer #14163
• starknet_transaction_prover: add --log-format text|json CLI flag #14162
• main

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