[issue 7] Add support of additional question types

[graceQUE03]

Changes

Changes are made to both frontend and backend that support for generating multiple types of questions.

Details of Changes

Note: FIB stands for fill-in-the-blank

• Server (rag-llm, app-constants): Prompts and validation follow question type: MC expects options A–D and letter correctAnswer; FIB expects text correctAnswer, acceptableAnswers, and no options. Normalization handles common LLM mistakes (e.g. loose answer + repair for MC). Stricter JSON-only instructions, retry hints, and more robust JSON extraction from noisy replies.
• Persistence (question service): Stores questionType and acceptableAnswers; updates support the same fields.
• Quiz / student APIs: Distinguishes types for transforms and shuffling (MC only); FIB checking via answerText where applicable; avoids treating FIB correctAnswer as an option letter.
• Client generation (generation-questions, llm-service, direct-ollama-service): Type-specific prompts and exports (CSV / QTI) for both shapes.
• Question generation page: Groups convert FIB items correctly; step-2 cards show question + correct answer (and acceptable variants) with edit paths for FIB.
• Question bank: Question type column; View/Edit modal branches on type (FIB vs MC).
• Settings: Prompt help text updated for dual types.
• FIB prompt style: Fill-in-the-blank stems as declarative unfinished sentences with a _________ blank (not WH-questions); examples include formula-style items.

Example

• In Question Generation page, support generating fill-in-the-blank questions. A declarative question with exactly one blank to fill is generated.

• In Question Bank page, all questions are listed with question type.

• When click on 'View/Edit Question' button of a FIB question, question (title), correct answer, and allowed answers are shown.

Student side

• Allow student to type down an answer and grading by clicking on 'Submit Answer' button.

- Able to grade students' answer against stored correct answer. - When student submits an incorrect answer for FIB question, displays correct answer at the bottom.