feat(backend): Activate domain events for user login, role assignment, and tenant removal

Implemented domain event raising in command handlers to enable audit logging and event-driven architecture for key Identity module operations.

Changes:
- Updated LoginCommand to include IpAddress and UserAgent fields for audit trail
- Updated AuthController to extract and pass IP address and user agent from HTTP context
- Modified LoginCommandHandler to raise UserLoggedInEvent on successful login
- Updated AssignUserRoleCommand to include AssignedBy field for audit purposes
- Modified AssignUserRoleCommandHandler to raise UserRoleAssignedEvent with previous role tracking
- Updated RemoveUserFromTenantCommand to include RemovedBy and Reason fields
- Modified RemoveUserFromTenantCommandHandler to raise UserRemovedFromTenantEvent before deletion
- Added domain methods to User aggregate: RecordLoginWithEvent, RaiseRoleAssignedEvent, RaiseRemovedFromTenantEvent
- Updated TenantUsersController to extract current user ID from JWT claims and pass to commands

Technical Details:
- All event raising follows aggregate root encapsulation pattern
- Domain events are persisted through repository UpdateAsync calls
- Event handlers will automatically log these events for audit trail
- Maintains backward compatibility with existing login flow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

colaflow-api/src/ColaFlow.API/Controllers/TenantUsersController.cs

@@ -64,7 +64,14 @@ public class TenantUsersController : ControllerBase
         if (userTenantId != tenantId)
             return StatusCode(403, new { error = "Access denied: You can only manage users in your own tenant" });
 
-        var command = new AssignUserRoleCommand(tenantId, userId, request.Role);
+        // Extract current user ID from claims
+        var currentUserIdClaim = User.FindFirst("user_id")?.Value;
+        if (currentUserIdClaim == null)
+            return Unauthorized(new { error = "User ID not found in token" });
+
+        var currentUserId = Guid.Parse(currentUserIdClaim);
+
+        var command = new AssignUserRoleCommand(tenantId, userId, request.Role, currentUserId);
         await _mediator.Send(command);
         return Ok(new { Message = "Role assigned successfully" });
     }
@@ -87,7 +94,14 @@ public class TenantUsersController : ControllerBase
         if (userTenantId != tenantId)
             return StatusCode(403, new { error = "Access denied: You can only manage users in your own tenant" });
 
-        var command = new RemoveUserFromTenantCommand(tenantId, userId);
+        // Extract current user ID from claims
+        var currentUserIdClaim = User.FindFirst("user_id")?.Value;
+        if (currentUserIdClaim == null)
+            return Unauthorized(new { error = "User ID not found in token" });
+
+        var currentUserId = Guid.Parse(currentUserIdClaim);
+
+        var command = new RemoveUserFromTenantCommand(tenantId, userId, currentUserId, null);
         await _mediator.Send(command);
         return Ok(new { Message = "User removed from tenant successfully" });
     }