refactor: add table primitive and migrations by date; feat: add mcp connectors

backend/migrations/20260517_tabular_review_document_ids.sql

@@ -0,0 +1,12 @@
+-- Migration date: 2026-05-17
+
+-- Persist selected document rows independently from generated cells.
+-- This lets project-based tabular reviews keep an explicit document list even
+-- when the review has no columns/cells or all rows have been removed.
+
+alter table public.tabular_reviews
+  add column if not exists document_ids jsonb;
+
+alter table public.tabular_reviews
+  alter column document_ids drop not null,
+  alter column document_ids drop default;