feat: replace native confirm() with custom styled dialog

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

index.html

@@ -586,6 +586,18 @@
   </div>
 </div>
 
+<!-- CONFIRM DIALOG -->
+<div class="edit-pl-overlay" id="confirm-overlay" onclick="if(event.target===this)_confirmCancel()">
+  <div class="confirm-box">
+    <div class="confirm-title" id="confirm-title"></div>
+    <div class="confirm-msg" id="confirm-msg"></div>
+    <div class="confirm-footer">
+      <button class="edit-pl-btn-cancel" onclick="_confirmCancel()">Abbrechen</button>
+      <button class="edit-pl-btn-delete" id="confirm-ok-btn" onclick="_confirmOk()">Bestätigen</button>
+    </div>
+  </div>
+</div>
+
 <!-- SONG INFO MODAL -->
 <div class="info-modal" id="info-modal">
   <div class="inner">