fix(backend): drop .js extension on @/ alias imports (embed/qdrant)

Backend uses extensionless @/ alias imports; the double .js caused
ERR_MODULE_NOT_FOUND at runtime (index.js.js).

services/backend/src/modules/messages/embed.ts

@@ -1,5 +1,5 @@
-import { config } from "@/shared/config/index.js";
-import { createChildLogger } from "@/shared/logger/index.js";
+import { config } from "@/shared/config/index";
+import { createChildLogger } from "@/shared/logger/index";
 
 const logger = createChildLogger("messages-embed");