docs: add topping category API descriptions (reject + get)

[zamani3270]

Summary

• add topping-category-reject-description.md
• add topping-category-activate-description.md
• add topping-category-deactivate-description.md
• add topping-categories-get-description.md
• add topping-categories-get-pending-description.md
• add topping-category-get-by-id-description.md
• add topping-categories-get-approved-description.md
• add topping-create-description.md
• add topping-update-description.md
• add topping-approve-chef-description.md
• add topping-reject-description.md
• add topping-get-description.md
• add topping-delete-description.md
• add topping-get-vendor-product-description.md
• add topping-get-approved-description.md
• add topping-get-pending-description.md
• add topping-get-by-category-description.md
• add topping-get-variants-description.md
• add topping-activate-description.md
• add topping-deactive-description.md
• add topping-assign-product-variants-description.md
• add product-variant-assign-topping-description.md
• rewrite topping-update-description.md for the new update contract (vendorId, name, price, stock) and updated response shape (isActive)
• adjust topping-approve-chef-description.md response example to match current contract (no tax, includes isActive)
• update topping-categories-get-approved-description.md to include optional name filter in query parameter docs and examples
• update topping-category-get-by-id-description.md to include optional name filter in query parameter docs and examples
• clarify route mapping with controller/action attributes for topping, topping-category, and product-variant assignment endpoints
• document Reject, Activate, Deactivate, Get All, Get Pending, Get By Id, Get Approved Topping Category, Create Topping, Update Topping, Approve Topping (Chef Users), Reject Topping, Get Topping, Delete Topping, Assign Topping To Product Variants, Activate Topping, DeActive Topping, Get Vendor Product Toppings, Get Approved Toppings, Get Pending Toppings, Get Toppings By Category, Get Topping Variants, and Assign Topping To Product Variant endpoints with field/reference tables, request samples, cURL examples, response examples, and status code summaries

Testing

• not applicable (documentation-only changes)