fix: email variable replacement + icon URL path

1. Added missing base variables in get_variables():
   - site_name, site_title, store_name
   - shop_url, my_account_url
   - support_email, current_year

2. Fixed social icon URL path calculation:
   - Was using 3x dirname which pointed to 'includes/' not plugin root
   - Now uses WOONOOW_URL constant or correct 4x dirname

3. Added px-6 padding to EmailBuilder dialog body

4. Added portal container to Select component for CSS scoping

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

@@ -391,7 +391,7 @@ export function RichTextEditor({
           </DialogHeader>
 
           <DialogBody>
-            <div className="space-y-4">
+            <div className="space-y-4 !p-4">
               <div className="space-y-2">
                 <Label htmlFor="btn-text">{__('Button Text')}</Label>
                 <Input