Fastify's fast-json-stringify was silently stripping message and statusCode from error responses because most route schemas only declared { error: string }. The global error handler sends { error, message, statusCode } but those extra fields never reached clients. - Add shared errorResponseSchema and sendError() helper in api-errors.ts - Replace 16 per-route errorJsonSchema definitions with the shared import - Split PDS + DB try/catch blocks in topics, replies, reactions so PDS failures return 502 (Bad Gateway) and local DB failures return 500 - Change auth session and setup service errors from 502 to 500 (local ops) - Update tests to match new response shape and status codes