Registry-ready patch release.\n\nChanges:\n- Add .tabularium metadata for the Tabularis plugin registry.\n- Add a DM plugin icon for registry/plugin-center display.\n- Bump plugin/package version to 1.0.1.\n- Document Plugin Center installation while keeping the Dameng JDBC driver user-provided.\n\nVerification:\n- mvn clean package passed: 63 tests.\n- Release zip checked to include .tabularium and assets/icon.svg.\n- Release zip does not include Dameng JDBC jars or JDBC zip files.