Misc bugs 2023-10 & 2024-04

Misc quick bugs & improvements: (see chat messages elsewhere)

• Notifications list page needs a Load More button, if there are really many. See instead: Can't scroll down in one's notification list, on iOS.
• Add a user list link, so simpler for admins to find the list of users.
• Link previews to categories shows the forum title instead of the category title. Fixed.
• Delete an auto-reply post —> Error — Fixed.
• Webhooks: Incl page category ID & reference ID — Fixed.
• API: Fetch a page by its Talkyard ID, or reference ID, TyE0450WKTD?
• /latest can be slow — PostgreSQL index missing? Fix: Hide Online status in users list or disable the feature? at the same time. — Now there's an index.
• "Home" doesn't always go to the correct view — sometimes to /latest instead of /categories — Fixed.