flatten app to repo root and update docker deployment for single-stack runtime

app/api/tasks/[taskId]/route.ts

@@ -0,0 +1,17 @@
+import { jsonError } from '@/lib/server/http';
+import { getTaskById } from '@/lib/server/tasks';
+
+type Context = {
+  params: Promise<{ taskId: string }>;
+};
+
+export async function GET(_request: Request, context: Context) {
+  const { taskId } = await context.params;
+  const task = await getTaskById(taskId);
+
+  if (!task) {
+    return jsonError('Task not found', 404);
+  }
+
+  return Response.json({ task });
+}