Do not allow creation of duplicated wishlist names

[Kibria-BS1954]

Title: System allows creation of duplicate wishlist names

Summary System allows creation of duplicate wishlist names which can create confusion to user when pop up appears for custom wishlist

Environment:

• nopCommerce version: 4.90
• Browser: [specify browser and version]
• User role: Logged-in customer

Preconditions:

• User must be logged in.

Steps to Reproduce:

1. Click “Create New Wishlist”.
2. Enter a wishlist name that already exists.
3. Click OK.

Expected Result:

• System should display an error message: “Wishlist name already exists” and prevent creating a duplicate.

Actual Result:

• System allows creating multiple wishlists with the same name.

Severity: Medium/Enhancement (affects core functionality of wishlists)

Priority: High (can confuse users and affect shopping experience)

Type: Functional

Screenshots / Attachments:
https://jam.dev/c/341b5805-8e20-4368-a849-49443e04002b