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

backend/migrations/20260424_02_docx_version_number_upload.sql

@@ -0,0 +1,31 @@
+-- Migration date: 2026-04-24
+
+-- Migration: number the original upload as V1 so assistant edits start at V2.
+-- Before: upload rows had version_number NULL, assistant_edit rows started at 1.
+-- After: every row in document_versions has a monotonic per-document V# with
+--        the upload as V1.
+
+-- Guard: this shift is not naturally idempotent (re-running would bump the
+-- numbers again). An unnumbered upload row is the signal that the migration
+-- has not run yet; once every upload row is numbered there is nothing to do.
+DO $$
+BEGIN
+  IF EXISTS (
+    SELECT 1 FROM public.document_versions
+    WHERE source = 'upload' AND version_number IS NULL
+  ) THEN
+    -- 1. Shift existing assistant_edit + user_upload numbers up by 1 so they no
+    --    longer collide with the upload's new V1. Done first so we don't violate
+    --    any uniqueness constraint while the upload row still lacks a number.
+    UPDATE public.document_versions
+    SET version_number = version_number + 1
+    WHERE source IN ('assistant_edit', 'user_upload')
+      AND version_number IS NOT NULL;
+
+    -- 2. Backfill every upload row's version_number to 1.
+    UPDATE public.document_versions
+    SET version_number = 1
+    WHERE source = 'upload'
+      AND version_number IS NULL;
+  END IF;
+END $$;