fix(selfhost): update docker db schema to match FileRecords (#3527)

In #2636, FileRecord was defined to have updated_at  field
which is used when it is accessed from the database. But the
local dev setup is missing this field.

This diff adds an updated_at column to match the expectation

docker/volumes/db/init/schema.sql

@@ -84,6 +84,7 @@ CREATE TABLE public.files (
   file_key text NOT NULL,
   file_size bigint NOT NULL,
   created_at timestamp with time zone NULL DEFAULT now(),
+  updated_at timestamp with time zone NULL DEFAULT now(),
   deleted_at timestamp with time zone NULL,
   CONSTRAINT files_pkey PRIMARY KEY (id),
   CONSTRAINT files_file_key_key UNIQUE (file_key),