style(登录页面): 为手机号和密码输入框添加必填标记和占位符

为提升用户体验，在手机号和密码输入框前添加红色星号标记表示必填项，并添加占位符提示用户输入格式

@@ -19,7 +19,7 @@
         <form class="space-y-6" @submit.prevent="handleSubmit">
           <div>
             <label for="mobile" class="block text-sm font-medium text-gray-700">
-              手机号
+              手机号 <span class="text-red-500">*</span>
             </label>
             <input
               id="mobile"
@@ -30,6 +30,7 @@
               required
               pattern="^1[3-9]\d{9}$"
               maxlength="11"
+              placeholder="请输入手机号"
               @input="mobile = $event.target.value.replace(/\D/g, '')"
               @focus="handleInputFocus"
               class="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-green-500 focus:border-green-500"
@@ -38,7 +39,7 @@
 
           <div>
             <label for="password" class="block text-sm font-medium text-gray-700">
-              密码
+              密码 <span class="text-red-500">*</span>
             </label>
             <input
               id="password"
@@ -47,6 +48,7 @@
               type="password"
               autocomplete="current-password"
               required
+              placeholder="请输入6位密码"
               class="mt-1 block w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-green-500 focus:border-green-500"
             />
           </div>