fix(mysql): match Community editor payload and metadata fidelity

[openai0229]

Summary

• Accept explicit-null Community table-editor payloads and the frontend IN_VALUES operation.
• Preserve UNSIGNED, empty and quoted ENUM/SET members, and composite primary-key order through native mysql_async metadata.
• Infer ordinary column moves from array order while rejecting generated, invisible, ZEROFILL, and other lossy live definitions.
• Return the six-option Community MySQL view editor template without requiring an existing view.

Verification

• make verify
• cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
• make native-mysql-integration against local Docker MySQL 8.4.8
• Chat2DB knowledge lint
• Zero fixture databases and zero Chat2DB Java processes after the final run

Constraints

• Original Community frontend and styles are unchanged.
• Native MySQL operations keep Java dormant.
• The macOS Package workflow was not triggered.

Closes #8