- create: auto-delete REJECTED→throw error; add tenantId filter
- remove: forbid PUBLISHED bank deletion
- removeItem: forbid PUBLISHED item deletion
- generateQuestions: restrict to DRAFT status only
- frontend: render MULTIPLE_CHOICE options/judgment/followupHints
- frontend: add judgment and followupHints to QuestionBankItem type
- add 12 service guard tests (109 total)