add build-frontend API endpoint

backend/app/main.py

@@ -1164,3 +1164,38 @@ async def serve_frontend_paths(path: str):
         return FileResponse(file_path)
     # 回退到 index.html (SPA 路由)
     return FileResponse(FRONTEND_DIR / "index.html")
+
+
+@app.post("/admin/build-frontend")
+async def build_frontend(background_tasks: BackgroundTasks):
+    """构建前端 (仅用于部署)"""
+    import subprocess
+    
+    frontend_path = FRONTEND_DIR.parent
+    
+    async def run_build():
+        try:
+            result = subprocess.run(
+                ["npm", "install"],
+                cwd=str(frontend_path),
+                capture_output=True,
+                text=True,
+                timeout=300
+            )
+            result = subprocess.run(
+                ["npm", "run", "build"],
+                cwd=str(frontend_path),
+                capture_output=True,
+                text=True,
+                timeout=300
+            )
+            return result.returncode == 0, result.stdout, result.stderr
+        except Exception as e:
+            return False, "", str(e)
+    
+    success, stdout, stderr = await run_build()
+    
+    if success:
+        return {"status": "success", "message": "前端构建成功"}
+    else:
+        return {"status": "error", "message": stderr or "构建失败"}