fix(tiptap-editor): use insertContentAt with drop position in onDrop handler

Previously dropped images were inserted at the current cursor position
instead of the actual drop position. Now uses insertContentAt(pos, ...)
to place images at the correct location.

libs/tiptap-editor/src/index.ts

@@ -78,7 +78,10 @@ class TiptapEditorInstance {
               files.forEach((file) => {
                 this.options.onImageUpload!(file)
                   .then((url) => {
-                    editor.chain().focus().setImage({ src: url }).run()
+                    editor.chain().focus().insertContentAt(pos, {
+                      type: 'image',
+                      attrs: { src: url }
+                    }).run()
                   })
                   .catch((err) => {
                     console.error('[TiptapEditor] Upload failed:', err)