bug: proxy: redact URL from reported errors

[joanestebanr]

Bug Report

The error fields and warning sometimes include the failed URL:

{
      "step_index": 3,
      "step_name": "WaitingClaim",
      "status": "error",
      "start_date": "2026-09-16T11:06:07.099788744+02:00",
      "error": {
        "error_type": 0,
        "error_type_string": "transient",
        "retry_count": 4,
        "description": [
          "claim status: Post \"http://1.2.3.4q :8545\": dial tcp 1.2.3.4:8545: connect: no route to host",
          "claim status: Post \"http://1.2.3.4:8545\": dial tcp 1.2.3.4:8545: connect: no route to host",
          "claim status: Post \"http://1.2.3.4:8545\": dial tcp 1.2.3.4:8545: connect: no route to host",
          "claim status: Post \"http://1.2.3.4:8545\": dial tcp 1.2.3.4:8545: connect: no route to host"
        ]
      }
    },