Fix responsive design - proper md: breakpoints for all screens

Fix all screens mobile layout - Room, Lobby, MainMenu compact for landscape

Fix mobile landscape layout - compact sizing and constraints

Fix TypeScript error with screen.orientation.lock

Add fullscreen button to landscape overlay, restore portrait detection

Remove unused isFullscreen state

Force visible fullscreen button and gradient background

Move fullscreen button to right center, add fallback bg color

Fix assets: copy to client/public, improve fullscreen button visibility

Remove unused useCallback import

Mobile fullscreen support and responsive layout improvements

Initial commit