Add AI assessment state with no-evidence detection for responses

Enhanced AI Assessment Tracking

• Responses and response choices now include an ai_assessment_state field that indicates the assessment status
• The Briink AI automatically detects when there is insufficient evidence to answer a question, marking responses with a NO_EVIDENCE state

Improved Retrieval Quality

• Document retrieval now returns 200x relevant context by default, improving answer quality for complex questions

Bug Fixes

• Fixed an issue with questionnaire question reordering that could cause validation errors when updating questions