Add IpV4Address (net)

[vhrcgcom]

Description

Implement IpV4Address as a ValueObject in the net module.

Spec: valid IPv4 (e.g. 192.168.1.1)

Implementation checklist

• Create src/net/ipv4address.rs
• Implement ValueObject trait
• Add #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
• Export from src/net/mod.rs and prelude
• Unit tests: valid input · empty input · invalid format · normalisation
• Doc comment with # Example block
• Update status in ROADMAP.md from ⬜ to ✅

Implementation detail

Input / Output

	Type	Alias
Input	String	IpV4AddressInput
Output	String — canonical dotted-decimal	IpV4AddressOutput

Normalization

Parse with std::net::Ipv4Addr, then re-serialise to its Display form (canonical dotted-decimal, no leading zeros).

Validation

Must parse successfully via std::net::Ipv4Addr::from_str. Leading zeros in octets are rejected (e.g. "192.168.01.1" is invalid — they cause ambiguity with octal notation).

Extra methods

• octets() -> [u8; 4]
• is_private() -> bool — true for RFC 1918 ranges (10.x, 172.16–31.x, 192.168.x).
• is_loopback() -> bool — true for 127.x.x.x.

References

• ROADMAP.md
• CONTRIBUTING.md