[Moonwalker-rgb]

Summary

• add authenticated dashboard aggregation endpoints for learner progress and activity
• add a responsive learner dashboard with progress, streaks, credentials, achievements, inferred skills, and course recommendations
• add focused component coverage for the dashboard

Verification

• focused learner dashboard test passes
• new dashboard files introduce no additional TypeScript errors
• repository-wide checks retain unrelated pre-existing failures on the base branch

Closes #416