feat: add theme translation keys for light, dark, and system modes in multiple locales

src/locales/zh.json

@@ -280,6 +280,9 @@
   "Verge Advanced Setting": "Verge 高级设置",
   "Language": "语言设置",
   "Theme Mode": "主题模式",
+  "theme.light": "浅色",
+  "theme.dark": "深色",
+  "theme.system": "系统",
   "Tray Click Event": "托盘点击事件",
   "Show Main Window": "显示主窗口",
   "Show Tray Menu": "显示托盘菜单",
@@ -564,4 +567,4 @@
   "Failed to save settings": "端口设置失败",
   "TCP Concurrency": "TCP并发",
   "TCP ConcurrencyWhen accessing a web page, DNS resolution generally results in multiple IP addresses.": "TCP 并发性当访问网页时，DNS 解析通常会产生多个 IP 地址。"
-}
+}