feat: add deletedAt collectionsInsightsProjects (CM-888)

[ulemons]

Summary

This PR introduces soft-deletion support for Collections Insights projects.

Changes

• Added deletedAt column to the collectionsInsightsProjects PostgreSQL table
• Added deletedAt field to the collectionsInsightsProjects Tinybird datasource

Rationale

Aligns database schema and analytics pipeline to support soft deletes and ensure consistent data handling across systems.

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Note

Enables soft deletion for collectionsInsightsProjects across storage and analytics.

• Adds migration to Postgres to introduce nullable deletedAt column on collectionsInsightsProjects
• Updates Tinybird datasource schema and description to include deletedAt (as Nullable(DateTime64(3))) aligned with the new column

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