Fix UnboundLocalError in fetch_v2fly_domains when domain file fails to parse

[msarg44]

Summary

BaseProvider.fetch_v2fly_domains() in cloudcheck/providers/base.py only assigns the local domains variable inside the try block:

errors = []
repo_path, _success = self._ensure_v2fly_repo_cached()
company_file = repo_path / "data" / self.v2fly_company
try:
    domains = parse_v2fly_domain_file(company_file)
except Exception as e:
    errors.append(
        f"Failed to parse {self.v2fly_company} domains: {e}:\n{traceback.format_exc()}"
    )
return sorted(list(domains)), errors

If parse_v2fly_domain_file() raises (e.g. the v2fly community repo clone fails, or the company's data/<company> file is missing/unreadable), the except branch correctly appends the error, but domains was never bound. The final return sorted(list(domains)), errors then raises UnboundLocalError, crashing the whole domain-update pass for the provider — even though a perfectly good error message was already collected.

Change

Initialize domains = set() before the try block so the failure path returns the collected error plus empty domains instead of crashing:

errors = []
domains = set()
repo_path, _success = self._ensure_v2fly_repo_cached()
company_file = repo_path / "data" / self.v2fly_company
try:
    domains = parse_v2fly_domain_file(company_file)
except Exception as e:
    errors.append(
        f"Failed to parse {self.v2fly_company} domains: {e}:\n{traceback.format_exc()}"
    )
return sorted(list(domains)), errors

This matches the documented contract (fetch_v2fly_domains() returns (domains, errors)) — downstream callers in update_domains() already handle per-provider errors gracefully.

Testing

Added a regression test test_v2fly_domains_missing_file in cloudcheck_update/test_cloudcheck_update.py that patches parse_v2fly_domain_file to raise, then asserts the call returns ([], [error]) rather than crashing with UnboundLocalError.