Analytics, pixel icons, and copy fixes

Added

• Gameplay analytics track screen views, auth, lobby actions, match start and end, and reconnects.

Changed

• Icons across the interface use the HackerNoon pixel set, and the bundled mono webfont is gone.
• Joining a code with no lobby now says so plainly, and the stray Italian main-menu button reads “Browse Lobbies”.

Fixed

• The sitemap answers HEAD requests, so search console validators stop seeing a 404.