fix: playlist cover upload — send raw image body not multipart

Navidrome expects Content-Type: image/* with raw binary body.
Bump SW to ns-v34.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.js

@@ -506,9 +506,10 @@ async function editPlCoverSelected(input){
   document.getElementById('edit-pl-cover').innerHTML=`<img src="${preview}" style="width:100%;height:100%;object-fit:cover">`;
   try{
     const token=await ndAuth();
-    const form=new FormData();form.append('image',file);
     const res=await fetch(`${cfg.url}/api/playlist/${_currentPlaylist.id}/image`,{
-      method:'POST',headers:{'X-Nd-Authorization':'Bearer '+token},body:form
+      method:'POST',
+      headers:{'X-Nd-Authorization':'Bearer '+token,'Content-Type':file.type||'image/jpeg'},
+      body:file
     });
     if(!res.ok)throw new Error(res.status);
     toast('Cover aktualisiert');