fix: wait for watched files to finish being written (#17100) (#21180)

This makes the external library watcher wait for files in watched directories to finish being written before queuing jobs for each file.

server/src/services/library.service.ts

@@ -123,6 +123,10 @@ export class LibraryService extends BaseService {
       {
         usePolling: false,
         ignoreInitial: true,
+        awaitWriteFinish: {
+          stabilityThreshold: 5000,
+          pollInterval: 1000,
+        },
       },
       {
         onReady: () => _resolve(),