Forward-migrate persisted state on read instead of writing migration scripts (small JSON-file apps)

s&box: JSON serialization with Sandbox.Json — handles engine types that System.Text.Json misses

Flask routes crashed when request JSON parsed to None before data.get calls

Flask API crashed when handlers called .get on missing JSON request body

Flask JSON null body caused AttributeError on route payload access

Flask request handlers crash when JSON body is null and code calls data.get