feat(api): Settings API 支持字体大小设置

- GET 接口返回 fontSize 字段
- PUT 接口支持更新 fontSize 设置
- 添加字体大小范围限制 (12-20)

src/app/api/settings/route.ts

@@ -21,6 +21,7 @@ export async function GET() {
         temperature: '0.7',
         theme: 'light',
         language: 'zh-CN',
+        fontSize: 15,
         enableThinking: false,
         saveChatHistory: true,
       });
@@ -36,6 +37,7 @@ export async function GET() {
       temperature: settings.temperature || '0.7',
       theme: settings.theme,
       language: settings.language,
+      fontSize: settings.fontSize || 15,
       enableThinking: settings.enableThinking,
       saveChatHistory: settings.saveChatHistory,
     });
@@ -61,6 +63,7 @@ export async function PUT(request: Request) {
       temperature,
       theme,
       language,
+      fontSize,
       enableThinking,
       saveChatHistory,
     } = body;
@@ -110,6 +113,11 @@ export async function PUT(request: Request) {
       updateData.language = language;
     }
 
+    if (fontSize !== undefined) {
+      // 限制字体大小在 12-20 之间
+      updateData.fontSize = Math.min(20, Math.max(12, fontSize));
+    }
+
     if (enableThinking !== undefined) {
       updateData.enableThinking = enableThinking;
     }
@@ -151,6 +159,7 @@ export async function PUT(request: Request) {
       temperature: updatedSettings?.temperature || '0.7',
       theme: updatedSettings?.theme,
       language: updatedSettings?.language,
+      fontSize: updatedSettings?.fontSize || 15,
       enableThinking: updatedSettings?.enableThinking,
       saveChatHistory: updatedSettings?.saveChatHistory,
     });