Badge Trigger System 4.3

[Sheep4545]

• 🎉 New feature (Extends application, non-breaking feature)

PR Summary

Implements backend badge trigger logic that evaluates user engagement stats against configured badge rules and automatically persists newly earned badges to public.user_badges without duplicating awards.

Overview

• What feature/problem does this PR address?

Adds automatic badge awarding when users earn XP / progress streaks, so achievements are granted consistently and stored in the database.

• What approach was taken?

Added a modular badge trigger service (backend/services/badge_trigger.py) with a registry of badge conditions keyed by badge slug.
Wired badge evaluation into existing gamification event flows after XP is applied (/api/v1/quiz/result, /api/v1/flashcards/session-complete).
Persisted awards to public.user_badges and prevented duplicates by checking existing awards and relying on the (user_id, badge_id) primary key.

• Any important design decisions or trade-offs?

Badge rules are defined in a centralized registry for easy extension (new badge = DB row + new condition entry).
Awarding emits server logs on success for traceability.

Checklist

• Added a clear description
• Included evidence of Unit Testing: pytest (backend) passing: 146 passed
• Updated domentation (if needed)

Additional Notes

Manual testing performed (sample events):
Triggered quiz completion XP and verified new badge grants persisted to public.user_badges (getting_started, first_xp, 50_xp).
Replayed the same event and confirmed no duplicate badge awards (new_badges=[]).
Triggered flashcard session XP and confirmed no unexpected additional badges.

Jira Ticket

Jira Ticket(s) - [SOC-23]

[greptile-apps]

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