Add page flow for the identify as a smoker journey

[simonwhatley]

Updates the prototype_v4_3 smoking flow so tobacco type selection happens immediately after the phone questionnaire, with current-smoking status handled before demographic questions.

View prototype: https://lung-health-check-pr-79.herokuapp.com/prototype_v4_3/start-page

Changes include:

• Routes phone-questionnaire users to smoking-type.
• Updates smoking-type question label.
• Adds new smoking-status-current page for users who select multiple tobacco types.
• Keeps smoking-status for users who select one tobacco type.
• Moves smoking-duration into the per-tobacco loop after height and weight.
• Stores smoking duration answers per tobacco type.
• Uses present or past tense based on:
  • single type: smoking-status
  • multiple types: smoking-status-current
• Skips smoking-change and tobacco-smoking-change for shisha.
• Updates check-your-answers to show per-type duration answers and multi-type current-smoking status.