Design Dashboard Schema, Versioning & Search

Description: Define the Postgres schema for dashboards, including:

• dashboards table with JSONB config, lock_version, created/updated metadata.
• dashboard_versions table to store historical versions with partitioning/archiving strategy.
• search_vector column and GIN index for name-based search (start simple; extend later if needed).
• Ensure schema supports optimistic locking, auditing, compliance, and future scalability.

Acceptance Criteria:

• dashboards table created with JSONB config, lock_version, created_by, updated_by, timestamps.
• dashboard_versions table supports rollback and historical storage, with partitioning or archiving strategy considered.
• GIN index on search_vector column for dashboard name search implemented.
• Schema reviewed and approved by architecture team.
• Future-proof for additional search fields and version growth.