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
Logging-only hardening with no change to RPC behavior, config validation, or how URLs are stored or used at runtime.

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

Startup now emits a structured banner (version, git SHA, chain id, redacted RPC host, fee-validation and blocking-check flags, OHTTP) instead of risking full URLs or other sensitive config in log sinks.

CLI override messages for rpc_node_url and blocking_check_url route through the helper; empty default RPC URL is shown as <unset> rather than a misleading invalid placeholder. Unit tests cover credentials, paths, queries, fragments, and invalid/empty input.

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[reviewable-StarkWare]

This change is 

[avi-starkware]

• starknet_transaction_prover: document observability surface in README #14203
• starknet_transaction_prover: origin-level breadcrumbs for validation errors #14172
• starknet_transaction_prover: /health returns 503 when service is saturated #14171
• starknet_transaction_prover: bump prover_panics_total on panic hook fire #14170
• starknet_transaction_prover: HTTP request count + latency + in-flight metrics #14169
• 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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[einat-starkware]

@einat-starkware reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on avi-starkware).

[avi-starkware]

@avi-starkware reviewed 1 file and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on avi-starkware).