fix: email buttons now render with inline styles for Gmail

1. EmailRenderer: Added button parsing with full inline styles
   - Buttons now use table-based layout for email client compatibility
   - Solid and outline button styles with custom colors from settings

2. DefaultTemplates: Updated new_customer template
   - Added 'Set Your Password' button for auto-registered users
   - Uses {set_password_url} variable for password reset link

3. EmailRenderer: Added set_password_url variable
   - Generates secure password reset link for new customers
   - Also added my_account_url and shop_url to customer variables

includes/Email/DefaultTemplates.php

@@ -196,13 +196,16 @@ Your account is ready. Here\'s what you can do now:
 ✓ Easy returns and refunds
 [/card]
 
-[button url="{my_account_url}"]Access Your Account[/button]
-[button url="{shop_url}"]Start Shopping[/button]
+[card type="warning"]
+**Important:** Please set your password to access your account:
 
-[card type="info"]
-💡 **Tip:** Check your account settings to receive personalized recommendations based on your interests.
+[button url="{set_password_url}" style="solid"]Set Your Password[/button]
+
+This link will expire in 24 hours. Once set, you can log in anytime.
 [/card]
 
+[button url="{shop_url}" style="outline"]Start Shopping[/button]
+
 [card type="basic"]
 Got questions? Our customer service team is ready to help: {support_email}
 [/card]';