Remove `top_n_*`, `description_*`, `column_description`, `csv_column_extra` PostgresQL tables from PostgresQL database

[minshao]

📌 Summary

The following legacy PostgreSQL tables are scheduled to be removed in the upcoming review-database v0.41.0 release:

• top_n_*
• description_*
• column_description
• csv_column_extra

These tables are no longer used in v0.40.0+ after migrating logic to the Table<'d, T>-based interface and deprecating direct Database::* accessors.

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⚠️ Required Action

🔔 All users must first upgrade to review-database v0.40.0 before migrating to v0.41.0 to avoid data loss.

• The v0.40.0 release provides a grace period where the database schema is still compatible with older storage patterns, but usage has already shifted to the new design.
• Direct removal in v0.41.0 will permanently drop any existing data stored in these tables.
• If a project has not yet been upgraded to 0.40.0 and is relying on these tables, it will break once v0.41.0 is deployed.

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📣 Migration Notice

A migration notice should be issued alongside the release of v0.40.0 to notify users:

🚨 Notice: The review-database v0.41.0 release will drop deprecated PostgreSQL tables:
top_n_*, description_*, column_description, and csv_column_extra.
To avoid data loss, upgrade to v0.40.0 first and complete any required migration to file-based and Table<'d, T> APIs.

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✅ Tasks

• Add notification in CHANGELOG.md of v0.40.0 release
• Add runtime warning in v0.40.0 when deprecated tables are accessed (optional)
• Add migration script or dev tool to assist users in validating transition
• Drop tables in v0.41.0 migration script
• Finalize and tag v0.41.0