Проверить HTTP-ошибки хранения заданий

Beads: trasser-job-http-persistence. Depends on !63 (merged) -> !62 (merged) -> !61 (merged) -> !60 (merged). Three standalone MockMvc tests with real controller/advice/JobService and mocked storage: sanitized HTTP500 on submit/cancel/read failure, retry, no false success or export. No production-code changes. Java11/11 PASS, repeat MVC3/3 PASS, coverage16/16 PASS, docs1129/1129 PASS, catalogue221 VALID. Self-review found no blockers; not human acceptance. Limits: not TCP/PostgreSQL/crash/ambiguous commit/load/stand. Target parent branch only to isolate diff: DO NOT MERGE into parent. After dependencies integrated, retarget main and rerun CI. No merge or auto-merge requested. QA03b remains open.