feat: enhance Claude request header handling with append functionality

web/src/i18n/locales/en.json

@@ -85,6 +85,8 @@
     "Claude思考适配 BudgetTokens = MaxTokens * BudgetTokens 百分比": "Claude thinking adaptation BudgetTokens = MaxTokens * BudgetTokens percentage",
     "Claude设置": "Claude settings",
     "Claude请求头覆盖": "Claude request header override",
+    "Claude请求头追加": "Claude request header append",
+    "Claude会在原有请求头基础上追加这些值，不会覆盖已有同名请求头；重复值会自动忽略。": "Claude appends these values on top of existing request headers. Existing headers are not overwritten, and duplicate values are ignored automatically.",
     "Client ID": "Client ID",
     "Client Secret": "Client Secret",
     "Codex 授权": "",
@@ -1781,6 +1783,9 @@
     "格式化 JSON": "Format JSON",
     "格式正确": "Format Correct",
     "格式示例：": "Format example:",
+    "前：": "Before:",
+    "配置：": "Config:",
+    "后：": "After:",
     "格式错误": "Format Error",
     "检查更新": "Check for updates",
     "检测到 FluentRead（流畅阅读）": "FluentRead (smooth reading) detected",