feat(app): wire missing fe/be flows

[risu729]

Summary

• add typed app mutations for user/profile updates, avatar upload, and POI visits
• persist avatar and username edits through the API and render profile stats, perks, level, streak, and saved stickers from live data
• add POI check-in actions on web/native maps that call /api/pois/:id/visit and refresh quest progress

Checks

• bun run check