Add hidden library categories with a client-side lock

[manilkadev3-max]

Summary

• allow selected categories to be hidden from the library interface
• reveal hidden categories by entering an access code through Library search
• provide manual locking and an optional configurable timed relock
• store the preference through existing WebUI metadata

Scope

This feature provides client-side UI concealment for shared browser sessions. It is not an access-control boundary.

An authenticated user with API access or control over the browser can bypass the lock and access the underlying category data.

Testing

• pnpm format:check
• pnpm tsc
• pnpm lint
• pnpm build
• verified category configuration, correct and incorrect access codes, search-field unlocking, manual and automatic relocking, persistence, and desktop and mobile layouts

[schroda]

Client side password protection makes no sense. Anyone who has access to the server can just modify the client data

[manilkadev3-max]

Thank you for pointing this out. You are right that verification and filtering performed entirely by the client cannot provide an access-control boundary. I have updated the title, description, and user-facing wording to describe this as client-side concealment using an access code; it does not restrict server API access.

Would this explicitly limited scope be acceptable for the WebUI? If actual access control is required, would a fully server-backed implementation be within the project scope, with verification, unlock expiration, and category filtering enforced by Suwayomi-Server? Otherwise, I am happy to close this PR and keep the feature as a local customization.

[schroda]

I think making it possible to hide categories is enough. The whole "client side authentication" stuff is overkill