[kulmann]

Description

When a guest's session ended or their access to a share was removed while they had a file open in an app, the app treated it as a plain error:

• Opening a file showed a bare "Unknown error" page with no way back. Now a 401 while loading the file or its content is handed to the auth error handling, so a guest is sent to the renew page. A signed-in user whose token gets renewed has the file loaded once more, otherwise the error screen shows.
• Saving answered a guest with "You're not authorized to save this file". A guest now gets "Your access to this file has ended, so it cannot be saved. Copy your changes before you leave this page." and keeps the editor content.
• A 401 while downloading the file content wasn't recognised as an ended guest session, because getFileContents wraps the error into a plain HttpError. It now is.

Note for extension developers: HttpError.response in @opencloud-eu/web-client is now typed Response | AxiosResponse (it already held an AxiosResponse at runtime for getFileContents). Code reading fetch-only members such as .url or .json() needs to narrow the type first. DavHttpError.response stays Response.

How Has This Been Tested?

• test environment: unit tests (Vitest), not tested in a browser against a backend yet
• test case 1: AppWrapper: a 401 while loading the file, its content or a graph request is handed to the auth error handling; navigating away loads nothing more; one retry after a renewed user token; error screen when the page stays or loading fails again
• test case 2: AppWrapper: guest, user and public link messages for a 401 on save
• test case 3: guestSessionManager: a 401 wrapped into an HttpError counts as an ended guest session for guest endpoints only
• test case 4: authService: handleAuthError resolves only after the access denied navigation
• test case 5: messages store: the request id is logged for fetch, axios and plain-object headers