feat(api): add assigned_agent to Task model (MS22-DB-003, MS22-API-003) (#591)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/api/src/tasks/tasks.service.ts

@@ -67,6 +67,9 @@ export class TasksService {
       metadata: createTaskDto.metadata
         ? (createTaskDto.metadata as unknown as Prisma.InputJsonValue)
         : {},
+      ...(createTaskDto.assignedAgent !== undefined && {
+        assignedAgent: createTaskDto.assignedAgent,
+      }),
       ...(assigneeConnection && { assignee: assigneeConnection }),
       ...(projectConnection && { project: projectConnection }),
       ...(parentConnection && { parent: parentConnection }),
@@ -291,6 +294,9 @@ export class TasksService {
         if (updateTaskDto.parentId !== undefined && updateTaskDto.parentId !== null) {
           data.parent = { connect: { id: updateTaskDto.parentId } };
         }
+        if (updateTaskDto.assignedAgent !== undefined) {
+          data.assignedAgent = updateTaskDto.assignedAgent;
+        }
 
         // Handle completedAt based on status changes
         if (updateTaskDto.status) {