Fix admin panel mock data issues and implement comprehensive user management features

[Copilot]

Problem

The admin panel had several critical issues that prevented it from properly displaying real bot data and managing users effectively:

• Mock data fallbacks: The admin panel was using generateMockUsers() and generateMockActivity() fallback methods instead of displaying real bot data
• Incomplete user management: No way to view detailed user information, their vocabulary, learning progress, or activity history
• Limited bulk operations: Bulk word assignment was incomplete and couldn't target different user groups effectively
• Poor user experience: No comprehensive interface for admins to manage users and their learning data

Solution

This PR implements a complete overhaul of the admin panel with the following major improvements:

🎯 Eliminated All Mock Data

• Removed generateMockUsers() and generateMockActivity() fallback methods
• Fixed dashboard stats to show real numbers (0 if no data) instead of demo values like 156, 3420, etc.
• Implemented proper error handling with user-friendly messages instead of falling back to fake data

🔧 Comprehensive User Management

• Enhanced User Details Modal: Added tabbed interface with Overview, Words, and Activity sections
• Complete Word Viewing: Display all user words with translations, definitions, Leitner box numbers, review counts, and accuracy
• Advanced Filtering: Filter words by status (all, due for review, by specific box) with search functionality
• Manual Word Addition: Admins can add individual words to any user with smart language detection
• User Statistics: Detailed analytics including box distribution, language pairs, study progress, and activity metrics

🚀 Enhanced Bulk Word Assignment

• Multi-language Support: Expanded from 4 to 14 languages (English, Spanish, French, German, Italian, Russian, Chinese, Japanese, Korean, Arabic, Persian, Hindi, Portuguese, Turkish)
• Flexible User Targeting:
  • All users
  • Active users only
  • Specific user selection with checkbox interface
• Complete Integration: Words are now actually assigned to users automatically after AI processing
• Better UI Organization: 3-column layout with configuration, user selection, and results

📊 User Activity Timeline

• New API Endpoint: /admin/users/{id}/activity provides comprehensive activity tracking
• Activity Types: Registration events, word additions, study sessions, learning progress
• Rich Metadata: Word lists, review performance, box progressions, accuracy statistics
• Interactive Timeline: Visual interface with color-coded activities, timestamps, and detailed information

🎨 Improved User Experience

• Professional Interface: Modern, responsive design with intuitive navigation
• Real-time Feedback: Toast notifications for all user actions with proper error handling
• Performance Optimizations: Efficient data loading and caching to handle larger user bases
• Accessibility: Better keyboard navigation and screen reader support

Technical Implementation

API Enhancements

// New comprehensive user details endpoint
GET /admin/users/{id} 
// Returns: user info, all words, box distribution, language breakdown, statistics

// New user activity timeline endpoint  
GET /admin/users/{id}/activity
// Returns: chronological activity feed with metadata and statistics

// Enhanced bulk word assignment
POST /admin/bulk-words-ai
// Now supports: flexible user targeting, automatic assignment, 14 languages

Database Integration

• Utilizes existing bot data structures without requiring schema changes
• Efficient querying with pagination and caching to handle KV storage limits
• Real-time statistics calculation from actual user cards and review data

Frontend Architecture

• AlpineJS reactive components for dynamic user interactions
• Modular modal design with lazy-loading for performance
• Responsive grid layouts optimized for different screen sizes

Impact

This completely transforms the admin panel from a demo interface into a professional-grade management system:

• 100% Real Data: All displayed information comes from actual bot usage
• Complete User Oversight: Admins can now view and manage every aspect of user learning
• Scalable Operations: Bulk word assignment works efficiently for any number of users
• Rich Analytics: Deep insights into user behavior and learning patterns
• Production Ready: Professional interface suitable for real-world bot administration

The admin panel now provides administrators with complete visibility and control over the Telegram bot's operation, user management, and learning content distribution.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[tayden1990]

Good Job