MySQL Community table DDL retrieval parity

[openai0229]

Summary

• add native MySQL SHOW CREATE TABLE retrieval through mysql_async
• map both Community table-DDL export aliases through Axum and desktop dispatch
• preserve all four pinned Community MySQL create/update example aliases as success with data: null
• correct the parity contract: Community exposes foreign keys as read-only metadata and does not implement foreign-key table mutation

Validation

• make verify
• make native-mysql-integration MYSQL_TEST_USER=root MYSQL_TEST_PASSWORD=root
• Core: 179 passed, 1 ignored
• Web: 52 passed, 1 ignored
• all three real local Docker MySQL 8.4 tests passed
• strict workspace Clippy passed
• knowledge lint passed
• Java remained dormant and fixture database count returned to zero
• original Community frontend and styles unchanged

Packaging

• macOS Package workflow was not triggered
• no local client package was built

Closes #10