feat(i18n): add header menu keys to all locales

Adds the header.* keys introduced by the header rewrite (enter, search
users, staff, mod/admin panel, command center, logs, logo generator,
dashboard/profile/settings links, credits/duckets/diamonds, ...) to all
25 message files. Values are translated where available and fall back to
English otherwise.

The working tree files had been re-serialized with escaped unicode
(\uXXXX); this commit restores literal UTF-8 so the diff shows only the
content change instead of a full-file rewrite.

src/messages/sr.json

@@ -42,7 +42,26 @@
 		"tagline": "An online virtual world where you can create your own avatar, make friends, chat, create rooms and much more!",
 		"login": "Логин",
 		"or": "Ор",
-		"createAccount": "Направите налог"
+		"createAccount": "Направите налог",
+		"enter": "Enter",
+		"searchUsers": "Претражи кориснике...",
+		"staff": "Особље",
+		"modPanel": "Mod panel",
+		"adminPanel": "Admin panel",
+		"commandCenter": "Цоммандоцентрум",
+		"logs": "Logs",
+		"logoGenerator": "Logo generator",
+		"myDashboard": "My dashboard",
+		"myProfile": "My profile",
+		"userSettings": "Settings",
+		"twoFactor": "Two-factor",
+		"loginActivity": "Login activity",
+		"friendRequests": "Friend requests",
+		"more": "+{count} висе",
+		"logout": "Одјава",
+		"credits": "Credits",
+		"duckets": "Duckets",
+		"diamonds": "Diamonds"
 	},
 	"footer": {
 		"copyright": "© {year} - {hotel} is a not for profit educational project"