[Bug] Dashboard stats are hardcoded — not fetched from API

[karastoyanov]

🐛 Bug Description

The Dashboard displays XP Points (1,200), Completed challenges (15), and Rank (24) as hardcoded strings. The GET /api/users/<user_id> endpoint already returns real xp, level, rank, and level_percentage data, but Dashboard never calls it.

📋 Steps to Reproduce

1. Log in and navigate to /dashboard
2. Complete a quest (XP should increase)
3. Observe that the dashboard stats remain 1,200 XP / 15 Completed / 24 Rank

🎯 Expected Behavior

Stats reflect the authenticated user's real data from GET /api/users/<user_id>.

📸 Actual Behavior

Hardcoded values in Dashboard.jsx:119-124 and the XP progress bar at Dashboard.jsx:229.

🌍 Environment

All environments.

📎 Additional Context

The /api/users/<user_id> route in users_routes.py:27 already returns xp, level, rank, level_percentage. The authUser.id is available from useAuth().