Reorganise the prototype to use a central file for question data

[simonwhatley]

Updated the prototype (v4.1) to use YAML-based question content and a shared question renderer. This means there is a central place where all content can be managed.

A future piece of work may introduce a YAML-based rules file so that we can manage the logic in YAML rather than JavaScript.

View deployment: https://lung-health-check-pr-70.herokuapp.com/

Details of the changes:

• Added central question content in app/prototype_v4_1/data/questions.yaml.
• Added tobacco-specific content in app/prototype_v4_1/data/tobacco.yaml.
• Added a shared question loader in app/prototype_v4_1/lib/questions.js.
• Added reusable validation in app/prototype_v4_1/lib/question-validator.js.
• Added support for:
  • radios
  • checkboxes
  • text inputs
  • date inputs
  • grouped inputs
  • conditional reveal inputs
  • contextual error messages
• Moved question pages to the shared _question.html renderer.
• Removed old question templates that are now rendered from YAML.
• Kept only bespoke templates for pages that are not standard questions, such as exit and not eligible pages.
• Split controller helper logic into smaller files:
  • eligibility.js
  • question-renderer.js
  • summary.js
  • tobacco-flow.js
  • unit-navigation.js
• Refactored question.js so it mainly contains route handlers.
• Moved tobacco type content, smoking change content, and shisha setting content out of the controller.
• Replaced string-based tobacco tense logic with explicit current and past content variants.
• Added contextual tobacco headings and errors for each tobacco type.
• Added frequency-aware wording for tobacco quantity questions, such as day, week, month or year.
• Added JSDoc comments to the main controller and library files.

[nataliariley]

Looks great thanks Simon