[snapetech]

Description

Adds a bounded, read-only failureReason to media requests. Movie and TV dispatch failures now store stable categories without persisting raw provider messages. The reason is cleared when an administrator changes the destination and resubmits, when a request is retried, or when media completes.

This independently adapts the request-failure categorization discussed in Seerr PR #3493 to SeerrNG’s request model and migration conventions. It is stacked on SeerrNG PR #262, which handles safe recovery for missing or mismatched TVDB identity. This PR does not add the separate user-facing failure explanation UI from Seerr PR #3494.

Also updates the request-status documentation and OpenAPI schema. Codex assisted with implementation and tests; the contributor reviewed the resulting changes.

How Has This Been Tested?

• pnpm test:node server/migration/sqlite/1791140000000-AddMediaRequestFailureReason.test.ts server/test/MediaRequestSubscriber.test.ts server/routes/request.test.ts server/subscriber/MediaSubscriber.test.ts — 259 passed.
• pnpm test:node server/routes/request.openapi.test.ts server/migration/sqlite/1791140000000-AddMediaRequestFailureReason.test.ts — 9 passed.
• pnpm typecheck:server — passed.
• Focused ESLint, Oxlint, Prettier, and git diff --check — passed.
• Full Mode 2 hosted validation is pending on this draft. No live provider round-trip or visual check applies to this backend/API change.

Screenshots / Logs (if applicable)

No UI changes.

Release Notes

• I added a release-note fragment under release-notes/.
• This change is internal-only and does not need a user-facing release note.
• The fragment includes audience, area, action, and breaking-change status.
• I previewed the release text with pnpm release-notes:preview.

Checklist:

• I have read and followed the contribution guidelines.
• Disclosed use of AI (see the AI assistance policy).
• I have updated the documentation accordingly.
• All new and existing tests passed. (Focused affected suites passed; the complete repository suite has not been run locally.)
• Successful build pnpm build.
• Translation keys: no translation keys are changed by this backend/API and documentation change.
• Database migration added for SQLite and PostgreSQL.