v5.0.2

fix(install): load Netgen Layouts schema (nglayouts_* tables) in CoreInstaller::importSchema()

Add importNetgenLayoutsSchema() private method called at the end of importSchema(). Resolves 'no such table: nglayouts_rule_group' HTTP 500 on fresh installations. Gracefully skipped if netgen/layouts-core is not present in vendor. Supports MySQL, PostgreSQL, and SQLite.