[Story]: Knowledge checks at onboarding milestones

[adoLime]

User Story

As an onboardee, I want short knowledge checks at key points in my onboarding, so that I can confirm I understood something before moving on.

Context & Motivation

• Type: Functional
• Parent epic: 07 EPIC - Learning, Upskilling & Content Recommendation #56

Acceptance Criteria

• At a milestone, the user gets one or more short questions (e.g. multiple-choice or a short answer) before the next part unlocks.
• A wrong answer shows the correct one with a short explanation, and the milestone is not yet passed.
• Once all checks at a milestone are passed, the next phase unlocks.
• The questions are part of the onboarding path content (defined alongside the steps).

Sub-Tasks (by team)

• Backend — store checks + attempts, grade answers, gate milestone completion.
• Frontend — question UI (multiple-choice + short answer), result / explanation, block "next" until passed.
• AI — (later) optionally generate check questions from the path content.

Dependencies

• Builds on the onboarding data model ([Story]: Onboarding checklist data model #109) and the paths ([Story]: Hard-coded onboarding path per role #108).