chore: bump version to v2026.4.326 and update changelog}
- Update package.json version from v2026.4.325 to v2026.4.326
- Update build version references from v2026.4.324 to v2026.4.325 across documentation files (README.md, INSTALL.md, change-log.md, change-break.md, todo.md, artifacts/php-7.2-ubuntu.md, artifacts/screenshots.md)