refactor: eliminate code duplication and force exit on config error

Improve config loading error handling in frontend by extracting common
logic and enforcing safer exit behavior.

Changes:

1. Extract handleConfigLoadError() function (DRY principle)
   - Previously: Identical error handling code duplicated in two places
     * Event listener for "configLoadError"
     * Bootstrap polling via get_init_error command
   - Now: Single reusable function called by both code paths
   - Reduces code from 86 lines to 70 lines (-35 duplicates, +30 new)

2. Replace confirm() with forced exit (safer UX)
   - Previously: User could click "Cancel" leaving app in broken state
     * No tray menu initialized
     * No AppState managed (all commands would fail)
     * Window open but non-functional
   - Now: App automatically exits after showing error message
   - Rationale: When config is corrupted, graceful exit is the only safe option

3. Add TypeScript interface for type safety
   - Define ConfigLoadErrorPayload interface explicitly
   - Improves IDE autocomplete and catches typos at compile time
   - Makes payload structure self-documenting

Benefits:
- Cleaner, more maintainable code (single source of truth)
- Safer user experience (no half-initialized state)
- Better type safety and developer experience
- Easier to add i18n support in the future (one string to translate)

This addresses code review feedback items #1 and #2.

src/main.tsx

@@ -11,7 +11,7 @@ import { queryClient } from "@/lib/query";
 import { Toaster } from "@/components/ui/sonner";
 import { listen } from "@tauri-apps/api/event";
 import { invoke } from "@tauri-apps/api/core";
-import { confirm, message } from "@tauri-apps/plugin-dialog";
+import { message } from "@tauri-apps/plugin-dialog";
 import { exit } from "@tauri-apps/plugin-process";
 
 // 根据平台添加 body class，便于平台特定样式
@@ -26,27 +26,34 @@ try {
   // 忽略平台检测失败
 }
 
-// 监听后端的配置加载错误事件：仅提醒用户并在确认后退出，不修改任何配置文件
+// 配置加载错误payload类型
+interface ConfigLoadErrorPayload {
+  path?: string;
+  error?: string;
+}
+
+/**
+ * 处理配置加载失败：显示错误消息并强制退出应用
+ * 不给用户"取消"选项，因为配置损坏时应用无法正常运行
+ */
+async function handleConfigLoadError(
+  payload: ConfigLoadErrorPayload | null,
+): Promise<void> {
+  const path = payload?.path ?? "~/.cc-switch/config.json";
+  const detail = payload?.error ?? "Unknown error";
+
+  await message(
+    `无法读取配置文件：\n${path}\n\n错误详情：\n${detail}\n\n请手动检查 JSON 是否有效，或从同目录的备份文件（如 config.json.bak）恢复。\n\n应用将退出以便您进行修复。`,
+    { title: "配置加载失败", kind: "error" },
+  );
+
+  await exit(1);
+}
+
+// 监听后端的配置加载错误事件：仅提醒用户并强制退出，不修改任何配置文件
 try {
   void listen("configLoadError", async (evt) => {
-    const payload = evt.payload as { path?: string; error?: string } | null;
-    const path = payload?.path ?? "~/.cc-switch/config.json";
-    const detail = payload?.error ?? "Unknown error";
-
-    await message(
-      `无法读取配置文件：\n${path}\n\n错误详情：\n${detail}\n\n请手动检查 JSON 是否有效，或从同目录的备份文件（如 config.json.bak）恢复。`,
-      { title: "配置加载失败", kind: "error" },
-    );
-
-    const shouldExit = await confirm("现在退出应用以进行修复？", {
-      title: "退出确认",
-      okLabel: "退出应用",
-      cancelLabel: "取消",
-    });
-
-    if (shouldExit) {
-      await exit(1);
-    }
+    await handleConfigLoadError(evt.payload as ConfigLoadErrorPayload | null);
   });
 } catch (e) {
   // 忽略事件订阅异常（例如在非 Tauri 环境下）
@@ -57,24 +64,12 @@ async function bootstrap() {
   // 启动早期主动查询后端初始化错误，避免事件竞态
   try {
     const initError = (await invoke("get_init_error")) as
-      | { path?: string; error?: string }
+      | ConfigLoadErrorPayload
       | null;
     if (initError && (initError.path || initError.error)) {
-      const path = initError.path ?? "~/.cc-switch/config.json";
-      const detail = initError.error ?? "Unknown error";
-      await message(
-        `无法读取配置文件：\n${path}\n\n错误详情：\n${detail}\n\n请手动检查 JSON 是否有效，或从同目录的备份文件（如 config.json.bak）恢复。`,
-        { title: "配置加载失败", kind: "error" },
-      );
-      const shouldExit = await confirm("现在退出应用以进行修复？", {
-        title: "退出确认",
-        okLabel: "退出应用",
-        cancelLabel: "取消",
-      });
-      if (shouldExit) {
-        await exit(1);
-        return; // 退出流程
-      }
+      await handleConfigLoadError(initError);
+      // 注意：不会执行到这里，因为 exit(1) 会终止进程
+      return;
     }
   } catch (e) {
     // 忽略拉取错误，继续渲染