Booking Questions on Line Items

When a seller has configured booking questions for a service, those questions attach to the cart line item. Answers (single-select, multi-select, free text, number, image upload) are written back to the line item before checkout proceeds.

1. getCartItemQuestions(cartId, lineItemId) returns the question list.
2. UI renders a typed input per question (depending on question.type).
3. answerCartItemQuestion posts a body shaped by type (selected_option_ids / comment / number / image_file_id).
4. removeCartItemAnswer clears a previous answer if the user changes their mind.

• 404 from getCartItemQuestions is treated as 'no questions for this item' — booking proceeds without blocking.
• image_upload answers require a previously-uploaded file id; the upload itself is handled by the file/upload service, not this endpoint.
• Questions are stored per-line-item, so duplicating the same service into the cart twice creates two independent question sets.

• lib/src/core/services/cart_service.dart:727 // getCartItemQuestions
• lib/src/core/services/cart_service.dart:776 // answerCartItemQuestion
• lib/src/core/services/cart_service.dart:811 // removeCartItemAnswer

Cross-references the seller's booking_questions feature — the seller side defines them, the cart side records answers.