feat: add export settings for Word document generation

- Add export configuration (untranslated text color, page orientation)
- Add second page header option for multi-page exports
- Integrate export settings into main export flow
- Separate export settings page with visual preview

app/api/config/route.ts

@@ -1,5 +1,5 @@
 import { NextResponse } from "next/server";
-import { getConfig, saveDBConfig, saveAIConfig, type DBConfig, type AIConfig } from "@/lib/config";
+import { getConfig, saveDBConfig, saveAIConfig, saveExportConfig, type DBConfig, type AIConfig, type ExportConfig } from "@/lib/config";
 
 // GET /api/config - 获取完整配置
 export async function GET() {
@@ -18,11 +18,11 @@ export async function GET() {
 }
 
 // POST /api/config - 保存配置
-// Body 格式: { db?: DBConfig, ai?: AIConfig }
+// Body 格式: { db?: DBConfig, ai?: AIConfig, export?: ExportConfig }
 export async function POST(request: Request) {
   try {
     const body = await request.json();
-    const { db, ai } = body;
+    const { db, ai, export: exportConfig } = body;
 
     if (db) {
       saveDBConfig(db);
@@ -32,8 +32,12 @@ export async function POST(request: Request) {
       saveAIConfig(ai);
     }
 
+    if (exportConfig) {
+      saveExportConfig(exportConfig);
+    }
+
     // 如果同时发送了完整配置
-    if (!db && !ai && body.db === undefined && body.ai === undefined) {
+    if (!db && !ai && !exportConfig && body.db === undefined && body.ai === undefined && body.export === undefined) {
       // 可能是旧的扁平格式，尝试兼容
       if (body.apiKey !== undefined || body.baseUrl !== undefined || body.model !== undefined) {
         saveAIConfig({