Improve accessibility: add ARIA labels to chat and forum components

[Pokled]

Context

Nodyx should be usable with screen readers. Many interactive elements in the chat and forum views are missing proper ARIA attributes.

What needs to be done

1. Audit chat components for missing aria-label, role, and aria-live attributes
2. Add proper labels to buttons that only have icons (send, attach, emoji picker)
3. Add aria-live=\"polite\" to the chat message list for new message announcements
4. Ensure forum thread list items are properly labeled

Files to look at

• nodyx-frontend/src/lib/components/Chat*.svelte
• nodyx-frontend/src/routes/forum/

Skills needed

• HTML accessibility basics
• Svelte component editing
• No backend knowledge required