[copyberry]

Improve diagnostics for report attachment failures

Why

Skipped report attachments lacked diagnostic logs, and upload failures logged only the HTTP status. Transport error strings can also contain credential-bearing URLs.

What changed

• Log why attachments are skipped, including missing rollout files, non-regular files, size limits, rate limits, and upload deadlines.
• Log attachment failures at error level with the error chain and available HTTP status.
• Replace RouteAwareRequestError details with the failure class and timeout, connection, request, and body flags before logging, avoiding credential-bearing transport URLs.

[github-actions]

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