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V2 ALTERs all 6 b* columns across tUser/tStaff/tPermissionCategory/ tModule from TINYINT(1) to BIT(1). MySQL preserves data on the type change (0 → b'0', 1 → b'1') and indexes survive the modify. MyBatis-Plus entity Boolean fields and existing 'WHERE bDeleted = 0' queries continue to work — MySQL Connector/J 8.x maps BIT(1) ↔ Boolean automatically and accepts integer literals via implicit conversion. Verified: setup-test-db + mvn test → 149/149 pass with V2 applied. Also updates docs/03-数据库设计文档.md (schema SSoT) so the table descriptors say bit(1) instead of tinyint(1).
