Incorrect breadcrumb link path in Product Variant detail view

[thochoertler]

In the Admin Dashboard, when viewing a single Product Variant, the breadcrumb link pointing back to "Products" uses the wrong URL.
Actual path: /admin/product
Expected path: /admin/products

This results in a navigation error since the singular route does not exist.

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To Reproduce

1. Go to Admin Dashboard
2. Navigate to Catalog → Products
3. Open any Product
4. Select a Product Variant to open the variant detail view
5. Click the breadcrumb link labeled "Products"
6. Observe the incorrect URL /admin/product

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Expected behavior
The breadcrumb should link to /admin/products, matching the actual Products list route.

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Actual behavior
Breadcrumb incorrectly links to /admin/product, which is not a valid route.

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Environment (please complete the following information):

• @vendure/core version: 3.5.1
• Nodejs version: 22
• Database (mysql/postgres etc): postgres
• Operating System (Windows/macOS/Linux): MacOS
• Browser (if applicable): Safari
• Package manager (npm/yarn/pnpm): npm