fix: login at signin.dspy — works around ahserver filename conflict

wwwroot/index.html

@@ -102,7 +102,7 @@ async function doLogin(){
  if(!u||!p){document.getElementById('login-msg').textContent='请输入用户名和密码';return}
  var fd=new FormData();fd.append('username',u);fd.append('password',p);
  try{
-  var r=await fetch('/pccs/api/do_login.dspy',{method:'POST',body:fd});
+  var r=await fetch('/pccs/api/signin.dspy',{method:'POST',body:fd});
   var d=await r.json();
   if(d.status==='ok'){closeLogin();document.getElementById('login-msg').textContent=''}
   else document.getElementById('login-msg').textContent=d.message||'登录失败'