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

backend/migrations/20260419_tabular_chat_jsonb.sql

@@ -0,0 +1,32 @@
+-- Migration date: 2026-04-19
+
+-- Migration: Convert tabular_review_chat_messages.content from TEXT to JSONB
+-- and add annotations JSONB column.
+--
+-- User messages:     content TEXT → JSON string  (e.g. "hello" → '"hello"')
+-- Assistant messages: content TEXT → events array (e.g. "answer" → '[{"type":"content","text":"answer"}]')
+--
+-- Only convert while content is still TEXT. Re-running over jsonb content would
+-- double-wrap assistant events, so the type check makes this safe to re-run.
+DO $$
+BEGIN
+  IF (
+    SELECT data_type
+    FROM information_schema.columns
+    WHERE table_schema = 'public'
+      AND table_name = 'tabular_review_chat_messages'
+      AND column_name = 'content'
+  ) = 'text' THEN
+    ALTER TABLE tabular_review_chat_messages
+      ALTER COLUMN content TYPE jsonb
+      USING CASE
+        WHEN role = 'user'
+          THEN to_jsonb(content)
+        ELSE
+          jsonb_build_array(jsonb_build_object('type', 'content', 'text', content))
+      END;
+  END IF;
+END $$;
+
+ALTER TABLE tabular_review_chat_messages
+  ADD COLUMN IF NOT EXISTS annotations jsonb;