fix template loop references

src/app/modules/songs/song/edit/edit-file/edit-file.component.html

@@ -25,7 +25,7 @@
     </button>
   </div>
 
-  @for (file of files$ | async; track file) {
+  @for (file of files$ | async; track file.id) {
     <p>
       <app-file [file]="file" [songId]="songId"></app-file>
     </p>

src/app/modules/songs/song/edit/history/history.component.html

@@ -1,6 +1,6 @@
 @if (song && song.edits) {
   <app-card heading="letzte Änderungen">
-    @for (edit of song.edits; track edit) {
+    @for (edit of song.edits; track edit.username + '-' + edit.timestamp.toMillis()) {
       <div class="list">
         <div>{{ edit.username }}</div>
         <div>{{ edit.timestamp.toDate() | date: "dd.MM.yyyy" }}</div>