feat: add assigneeId/assigneeName to tasks schema and API

- Added assignee_id and assignee_name columns to tasks table
- PATCH /api/tasks/:id now accepts assigneeId and assigneeName
- db:push on startup will auto-migrate the columns

backend/src/routes/tasks.ts

@@ -231,6 +231,8 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
       }
       if (body.priority !== undefined) updates.priority = body.priority;
       if (body.position !== undefined) updates.position = body.position;
+      if (body.assigneeId !== undefined) updates.assigneeId = body.assigneeId;
+      if (body.assigneeName !== undefined) updates.assigneeName = body.assigneeName;
 
       const updated = await db
         .update(tasks)
@@ -255,6 +257,8 @@ export const taskRoutes = new Elysia({ prefix: "/api/tasks" })
         status: t.Optional(t.String()),
         priority: t.Optional(t.String()),
         position: t.Optional(t.Number()),
+        assigneeId: t.Optional(t.Union([t.String(), t.Null()])),
+        assigneeName: t.Optional(t.Union([t.String(), t.Null()])),
       }),
     }
   )