feat(client): polished toolbar, live online count via SSE

- Redesign in-game client toolbar with refined glass styling and buttons
- Live online count + emulator status streamed over SSE multicast
- Who's-online tooltip throttled to reduce repeated requests
- Fix show button so it always returns the hidden toolbar
- Use theme CSS variables instead of hardcoded colors
- Add toolbar translations across all 25 locales

src/messages/de.json

@@ -3263,5 +3263,18 @@
 			"button": "Verify email",
 			"fallback": "If the button doesn't work, paste this link into your browser:"
 		}
+	},
+	"toolbar": {
+		"home": "Startseite",
+		"reload": "Neu laden",
+		"fullscreen": "Vollbild",
+		"logout": "Abmelden",
+		"onlineUsers": "Nutzer online",
+		"emulatorOnline": "Emulator online",
+		"emulatorOffline": "Emulator offline",
+		"dragToMove": "Ziehen zum Verschieben",
+		"hide": "Leiste ausblenden",
+		"fullscreenExit": "Vollbild beenden",
+		"show": "Leiste anzeigen"
 	}
 }