fix: correct frontend dist path to dist/public

artifacts/api-server/src/app.ts

@@ -47,7 +47,7 @@ app.use("/v1", openaiRouter);
 app.use("/api/v1", openaiRouter);
 
 // 提供前端靜態檔案
-const frontendDistPath = path.join(__dirname, "../../image-gen/dist");
+const frontendDistPath = path.join(__dirname, "../../image-gen/dist/public");
 app.use(express.static(frontendDistPath));
 
 // SPA fallback - 所有非 API 路由都返回 index.html