Add comprehensive error handling tests for two pure functions:
renderWebhookURL (8 new test cases):
- Empty/whitespace URL template validation
- Invalid template syntax (unclosed braces, undefined functions)
- Template producing empty URL
- Missing scheme or host in rendered URL
UpdateAllowedPrivateCIDRs (expanded from 8 to 29 cases):
- Invalid IP addresses (garbage, out of range, malformed)
- Invalid CIDR notation (prefix too large, negative, non-numeric)
- Malformed strings (double slash, invalid IP with valid prefix)
- Success cases for valid IPv4/IPv6 CIDRs and bare IPs
e6b9bd501d