fix: admin teams fetch produces excessive warnings for large orgs

[raiderrobert]

Problem

When running ownrs org <org> --refresh, the admin teams fetch produces hundreds of warning lines to stderr:

Warning: failed to fetch teams for <org>/<repo>: GitHub
Warning: failed to fetch teams for <org>/<repo>: GitHub
Warning: failed to fetch teams for <org>/<repo>: GitHub
... (200+ lines)

This obscures the actual output and makes the tool noisy. These are expected 403 errors for repos the user doesn't have admin access to.

Root cause

In src/sources/fetcher.rs, fetch_admin_teams matches errors by checking if the error string contains the literal strings "403" or "404":

Err(e) => {
    let err_str = e.to_string();
    if err_str.contains("403") || err_str.contains("404") {
        break;
    }
    eprintln!("Warning: failed to fetch teams for {org}/{repo}: {e}");
    break;
}

This string-matching approach is fragile — the octocrab error type may not include the HTTP status code in its Display output, causing expected 403 errors to fall through to the warning branch.

Suggested fix

• Suppress or aggregate warnings — these are expected permission errors, not actionable. Options:
  • Silently return empty for all API errors (user simply doesn't have access)
  • Aggregate into a single summary line: Note: could not fetch admin teams for 200 repos (insufficient permissions)
  • Only print individual warnings in a --verbose mode