v4.1.0: JSON Output & Retry Bug Fix

Release Notes:

Adds --json flag for structured per-URL output and fixes an infinite retry loop when the API returns no job ID.

What's New

• --json flag for JSONL output — emits one JSON line per URL result to stdout. Logs go to stderr. Pipe to jq or redirect to a file for structured processing: archiver --json --log WARNING urls... > results.jsonl
• ArchiveResult dataclass and on_result callback — run_archive_workflow accepts an optional callback invoked on each URL completion, enabling custom result handling.
• Fixed infinite retry loop — when the API accepted a submission but returned no job_id, the attempt counter was reset, preventing the retry limit from ever being reached. The URL would re-queue indefinitely.