fix(messages): prevent double image paste in Quill editor

Use stopImmediatePropagation + capture phase to prevent Quill's
built-in clipboard handler from also inserting the image as base64.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/messages/compose.html

@@ -677,18 +677,19 @@
         .catch(function() { alert('Błąd połączenia'); });
     }
 
-    /* Handle paste with images (screenshots) */
+    /* Handle paste with images (screenshots) — capture phase to beat Quill's handler */
     quill.root.addEventListener('paste', function(e) {
         var items = (e.clipboardData || {}).items || [];
         for (var i = 0; i < items.length; i++) {
             if (items[i].type.indexOf('image') !== -1) {
+                e.stopImmediatePropagation();
                 e.preventDefault();
                 var file = items[i].getAsFile();
                 if (file) uploadImage(file);
                 return;
             }
         }
-    });
+    }, true);
 
     /* Sync Quill content to hidden textarea on every change */
     var textarea = document.getElementById('content');

templates/messages/view.html

@@ -636,13 +636,14 @@
         var items = (e.clipboardData || {}).items || [];
         for (var i = 0; i < items.length; i++) {
             if (items[i].type.indexOf('image') !== -1) {
+                e.stopImmediatePropagation();
                 e.preventDefault();
                 var file = items[i].getAsFile();
                 if (file) uploadImage(file);
                 return;
             }
         }
-    });
+    }, true);
 
     var textarea = document.getElementById('reply-content');
     quill.on('text-change', function() {