Separate framework and app migrations

Also add a new develop command: clear-db.

framework/develop.d/clear-db

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+# This file belongs to the framework.  You are not expected to modify it.
+
+set -eu
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT="$DIR/../.."
+
+cd "$ROOT/express"
+"$DIR"/../cmd.d/tsx develop/clear-db.ts "$@"