Adds a complete achievement system with gamification features across all user interactions.
**Database & Types:**
- Add UserAchievement model to track user progress and earned achievements
- Add achievement-related fields to User model (achievementPoints, currentStreak, lastStreakCheck)
- Add ACHIEVEMENT_UNLOCKED audit action type
- Define 62 achievements as TypeScript constants across 5 categories
**Achievement Categories:**
- Suggestions (15): First suggestion through ultimate curator milestones
- Likes (12): First like through legendary fan milestones
- Comments (12): First comment through review legend milestones
- Engagement (15): Login streaks and total activity tracking
- Reports (8): Valid reports and accuracy tracking
**Backend Implementation:**
- Create AchievementService with comprehensive checking logic
- Add achievement route with 6 API endpoints
- Integrate achievement checking into all user interaction points:
- Suggestions (create + accept)
- Likes (toggle)
- Comments (all 6 media types)
- Login streaks
- Reports (profile + comment)
- Update UserService to include achievement points in profiles
**Frontend Implementation:**
- Create AchievementService for API communication
- Create achievements page showing all 62 achievements with:
- Category filtering (All, Suggestions, Likes, Comments, Engagement, Reports)
- Tier-based styling (Bronze, Silver, Gold, Platinum, Diamond)
- Progress indicators for in-progress achievements
- Earned date display for completed achievements
- Add "Recent Achievements" section to user profiles
- Add "🏆 Achievements" link to header navigation
- Only show "View All" link on own profile
**Technical Features:**
- Real-time achievement checking on user actions
- Progress tracking to avoid recalculation
- Points system for gamification
- Tier-based gradient styling
- Leaderboard-ready architecture
Resolves#48
Co-Authored-By: Hikari <hikari@nhcarrigan.com>
