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

backend/migrations/20260423_02_docx_version_number.sql

@@ -0,0 +1,32 @@
+-- Migration date: 2026-04-23
+
+-- Migration: give each assistant-produced version of a document a
+-- monotonic per-document version number (V1, V2, …). Only
+-- `source = 'assistant_edit'` rows carry a number; the original upload
+-- and the ephemeral user_accept/user_reject rows stay NULL. Numbers are
+-- stable once written — accept/reject now overwrite bytes in place
+-- rather than insert new rows, so the sequence never has gaps.
+
+ALTER TABLE public.document_versions
+  ADD COLUMN IF NOT EXISTS version_number integer;
+
+-- Backfill: assign 1..N to the existing assistant_edit rows per doc,
+-- ordered by created_at ascending. Safe to re-run (only writes NULLs).
+WITH numbered AS (
+  SELECT
+    id,
+    ROW_NUMBER() OVER (
+      PARTITION BY document_id
+      ORDER BY created_at ASC
+    ) AS rn
+  FROM public.document_versions
+  WHERE source = 'assistant_edit'
+)
+UPDATE public.document_versions dv
+SET version_number = n.rn
+FROM numbered n
+WHERE dv.id = n.id
+  AND dv.version_number IS NULL;
+
+CREATE INDEX IF NOT EXISTS document_versions_doc_vnum_idx
+  ON public.document_versions (document_id, version_number);