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/sr.json

@@ -3262,5 +3262,18 @@
 			"button": "Verify email",
 			"fallback": "If the button doesn't work, paste this link into your browser:"
 		}
+	},
+	"toolbar": {
+		"home": "Почетна",
+		"reload": "Освежи",
+		"fullscreen": "Цео екран",
+		"logout": "Одјава",
+		"onlineUsers": "Корисници на мрежи",
+		"emulatorOnline": "Емулатор онлајн",
+		"emulatorOffline": "Емулатор офлајн",
+		"dragToMove": "Превуците да померите",
+		"hide": "Сакриј траку",
+		"fullscreenExit": "Изађи из целог екрана",
+		"show": "Прикажи траку"
 	}
 }