fix(frontend): 用 CSS text-security 替代 password 输入框，简化配额进度条 UI

- Input 组件 masked 模式改用 WebkitTextSecurity: disc 替代 type=password，
  避免浏览器密码管理器自动填充干扰
- LoginDialog/UserFormDialog/Settings/ProxyNodes 密码字段统一迁移到 masked 属性
- PoolManagement 配额进度条布局从 grid 改为 flex，移除未使用的
  getQuotaProgressDisplayClass/getQuotaProgressTooltip 函数

Close #249
Co-authored-by: AAEE86 <ppk0227@hotmail.com>

frontend/src/views/user/Settings.vue

@@ -107,7 +107,8 @@
               <Input
                 id="old-password"
                 v-model="passwordForm.old_password"
-                type="password"
+                type="text"
+                masked
                 class="mt-1"
               />
             </div>
@@ -116,7 +117,8 @@
               <Input
                 id="new-password"
                 v-model="passwordForm.new_password"
-                type="password"
+                type="text"
+                masked
                 :placeholder="getPasswordPolicyPlaceholder(passwordPolicyLevel)"
                 class="mt-1"
               />
@@ -138,7 +140,8 @@
               <Input
                 id="confirm-password"
                 v-model="passwordForm.confirm_password"
-                type="password"
+                type="text"
+                masked
                 placeholder="再次输入密码"
                 class="mt-1"
               />