#39 [Admin Panel] User Management API - Get User Details

Implement GET /api/v1/admin/users/<user_id> endpoint to get detailed user information. **API Specification:** - Endpoint: GET /api/v1/admin/users/<user_id> - Permission Required: manage_users - Path Parameter: user_id (UUID) - Response: Complete user object with all details **Response Fields:** - user_id, tenant_id, email, display_name - roles[] with permission details - is_active, is_email_verified - created_at, created_by, updated_at - last_login, last_login_ip - login_count, failed_login_count - mfa_enabled, mfa_type - metadata (JSONB) - recent_activity[] (last 10 actions) **Requirements:** - Validate user belongs to current tenant - Include computed permissions (from all roles) - Include recent audit log entries for this user - Return 404 if user not found **IMPORTANT:** Implement with ultra attention to details and correctness. **BEFORE CLOSING:** Take screenshot of user detail API response. Add comment summarizing implementation.