feat(mcp): подготовить сервер и доступ к приёмке

backend/drizzle/0032_flow_write_receipts.sql

@@ -0,0 +1,10 @@
+-- Immutable commit evidence shared by ingestion and REST/MCP fact rebuild.
+-- No raw flow payload, IP addresses, credentials or notification contents belong here.
+CREATE TABLE IF NOT EXISTS flow_write_receipts (
+  batch_id uuid PRIMARY KEY,
+  kind text NOT NULL CHECK (kind IN ('ingest', 'facts', 'rebuild')),
+  source_proof text NOT NULL CHECK (source_proof ~ '^[a-f0-9]{64}$'),
+  result jsonb NOT NULL CHECK (jsonb_typeof(result) = 'object' AND octet_length(result::text) <= 65536),
+  committed_at timestamptz NOT NULL DEFAULT now()
+);
+-- Receipts are intentionally not pruned: an owned unknown batch may still need them.