Function validate_bind_address 

pub fn validate_bind_address(addr: &str) -> Result<IpAddr, String>

Validate and parse a bind address string

Accepts:

• IPv4 addresses: “127.0.0.1”, “0.0.0.0”
• IPv6 addresses: “::1”, “::”
• Bracketed IPv6: “[::1]”
• “localhost” (resolves to 127.0.0.1)

Returns the parsed IpAddr or an error message.