Fix --from-curl redirect handling to match curl semantics

[ryanfowler]

Summary

• Make --from-curl disable redirects unless curl passed -L/--location.
• Use curl’s default redirect limit of 50 when -L is present and --max-redirs is omitted.
• Preserve explicit --max-redirs values, including 0 and -1, by tracking whether the flag was set.
• Add CLI and curl parser coverage for the redirect cases.

Testing

• Added unit tests for --from-curl redirect translation in internal/cli.
• Added parser coverage for explicit --max-redirs values in internal/curl.
• Verified with go test ./....