fix: resolve tiptap duplicate Link extension warning

StarterKit 3.10+ now includes Link by default. Our code was adding
Link.configure() separately, causing duplicate extension warning and
breaking the email builder visual editor modal.

Fixed by configuring StarterKit with { link: false } so our custom
Link.configure() with specific options is the only Link extension.

admin-spa/src/components/ui/rich-text-editor.tsx

@@ -45,7 +45,11 @@ export function RichTextEditor({
 }: RichTextEditorProps) {
   const editor = useEditor({
     extensions: [
-      StarterKit,
+      // StarterKit 3.10+ includes Link by default, so disable it here
+      // since we configure Link separately below with custom options
+      StarterKit.configure({
+        link: false,
+      }),
       Placeholder.configure({
         placeholder,
       }),
@@ -123,7 +127,7 @@ export function RichTextEditor({
 
   const addImage = () => {
     openWPMediaImage((file) => {
-      editor.chain().focus().setImage({ 
+      editor.chain().focus().setImage({
         src: file.url,
         alt: file.alt || file.title,
         title: file.title,
@@ -328,7 +332,7 @@ export function RichTextEditor({
               {__('Add a styled button to your content. Use variables for dynamic links.')}
             </DialogDescription>
           </DialogHeader>
-          
+
           <div className="space-y-4 py-4">
             <div className="space-y-2">
               <Label htmlFor="btn-text">{__('Button Text')}</Label>
@@ -339,7 +343,7 @@ export function RichTextEditor({
                 placeholder={__('e.g., View Order')}
               />
             </div>
-            
+
             <div className="space-y-2">
               <Label htmlFor="btn-href">{__('Button Link')}</Label>
               <Input
@@ -362,7 +366,7 @@ export function RichTextEditor({
                 </div>
               )}
             </div>
-            
+
             <div className="space-y-2">
               <Label htmlFor="btn-style">{__('Button Style')}</Label>
               <Select value={buttonStyle} onValueChange={(value: 'solid' | 'outline') => setButtonStyle(value)}>
@@ -376,7 +380,7 @@ export function RichTextEditor({
               </Select>
             </div>
           </div>
-          
+
           <DialogFooter>
             <Button variant="outline" onClick={() => setButtonDialogOpen(false)}>
               {__('Cancel')}