Fix IPv6 host:port stripping in virtual host matching via net.SplitHostPort

[Copilot]

stripHostPortForVhost used naive string manipulation to strip ports, causing IPv6 addresses like [::1]:5244 to pass through unmodified (port intact), breaking vhost domain matching for IPv6 listeners.

Changes

• server/handles/fsread.go: Replace strings.LastIndex/strings.Contains logic in stripHostPortForVhost with net.SplitHostPort + fallback

// Before — IPv6 with port was not stripped
func stripHostPortForVhost(host string) string {
    if idx := strings.LastIndex(host, ":"); idx != -1 {
        if !strings.Contains(host, "[") {  // [::1]:5244 skipped here
            return host[:idx]
        }
    }
    return host
}

// After — handles all host formats correctly
func stripHostPortForVhost(host string) string {
    if h, _, err := net.SplitHostPort(host); err == nil {
        return h
    }
    return host  // no port present — return as-is
}

Input	Before	After
example.com:5244	example.com ✓	example.com ✓
192.168.1.1:5244	192.168.1.1 ✓	192.168.1.1 ✓
[::1]:5244	[::1]:5244 ✗	::1 ✓
[2001:db8::1]:8080	[2001:db8::1]:8080 ✗	2001:db8::1 ✓

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