server: fix broken item neighbors API

[zhenghaoz]

No description provided.

[Copilot]

Pull Request Overview

This PR fixes the ReadCategories function to accept a default categories parameter, addressing broken item neighbors API behavior. The change allows different endpoints to specify appropriate default categories instead of always defaulting to an empty string.

• Modified ReadCategories function signature to accept a defaultCategories parameter
• Updated all callers to pass explicit default categories: []string{""} for most endpoints, nil for item neighbors and collaborative endpoints
• Ensures consistent category handling across different API endpoints

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
server/rest.go	Updated ReadCategories function signature and all its callers to pass appropriate default categories
master/rest.go	Updated calls to ReadCategories to include default categories parameter

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}