Activitypub-Federation has SSRF via 0.0.0.0 bypass in activitypub-federation-rust v4_is_invalid()

The v4isinvalid function in activitypub-federation-rust src/utils.rs does not check for Ipv4Addr::UNSPECIFIED 0.0.0.0. An unauthenticated attacker controlling a remote domain can point it to 0.0.0.0, bypass the SSRF protection introduced by the fix for CVE-2025-25194 GHSA-7723-35v7-qcxw, and reac...