feat(v4): add hash format validation (MD5, SHA-1, SHA-256, SHA-384, SHA-512)

[976520]

Summary

• Hash format validation, Base64 variants
• Core API functions: _md5(), _sha1(), _sha256(), _sha384(), _sha512()
• Mini API support
• Eng locale messages

Usage

import * as z from "zod/v4";

const md5Schema = z.md5();
md5Schema.parse("5d41402abc4b2a76b9719d911017c592");

const sha256Base64Schema = z.sha256Base64();
sha256Base64Schema.parse("XohImNooBHFR0OVvjcYpJ3NgPQ1qq73WKhHvch0VQtg="); 

Issue

#4956