refactor(frontend): 重构前端样式体系，统一资源路径与代码规范

1.  重构SCSS样式结构，将原有分散的样式文件整合到custom目录下，统一使用@use替代@import
2.  删除冗余的全局样式文件，将样式逻辑内联到对应组件或集中到core目录
3.  新增DOMPurify依赖，对富文本内容添加XSS防护
4.  修复metrics端点暴露的兼容性问题，优化启动banner样式
5.  移除无用的权限校验代码，重构工作流组件路径与命名
6.  优化样式混合宏与响应式布局，修复部分组件样式冲突

frontend/web/src/components/views/fa-login/FaLoginAccountForm.vue

@@ -222,6 +222,6 @@ defineExpose({
 });
 </script>
 
-<style scoped>
-@import "@styles/fa-login.css";
+<style scoped lang="scss">
+@use "@styles/custom/fa-login";
 </style>

frontend/web/src/components/views/fa-login/FaLoginForgetPanel.vue

@@ -111,6 +111,6 @@ defineExpose({
 });
 </script>
 
-<style scoped>
-@import "@styles/fa-login.css";
+<style scoped lang="scss">
+@use "@styles/custom/fa-login";
 </style>

frontend/web/src/components/views/fa-login/FaLoginMobilePanel.vue

@@ -196,64 +196,5 @@ onBeforeUnmount(() => {
 </script>
 
 <style scoped lang="scss">
-@import "@styles/fa-login.css";
-
-.login-mobile-flow {
-  margin-top: 1rem;
-}
-
-.login-mobile-otp-cell {
-  box-sizing: border-box;
-  flex: 1;
-  min-width: 0;
-  max-width: 48px;
-  height: 40px;
-  padding: 0;
-  font-size: 1rem;
-  font-weight: 500;
-  color: var(--el-text-color-primary);
-  text-align: center;
-  appearance: none;
-  outline: none;
-  background: var(--el-fill-color-blank);
-  border: 1px solid var(--el-border-color);
-  border-radius: 8px;
-  transition:
-    border-color 0.2s ease,
-    box-shadow 0.2s ease;
-
-  &:focus {
-    border-color: var(--el-color-primary);
-    box-shadow: 0 0 0 1px var(--el-color-primary) inset;
-  }
-}
-
-.login-mobile-sms-btn {
-  border-radius: 8px;
-}
-
-html.dark {
-  .login-mobile-otp-cell {
-    background: rgb(255 255 255 / 6%);
-    border-color: rgb(255 255 255 / 14%);
-
-    &:focus {
-      border-color: var(--el-color-primary);
-    }
-  }
-}
-
-/* EP 全局规则：相邻 .el-button { margin-left: 12px }，纵向叠放时仍会命中，导致第二颗按钮横向错位 */
-.login-mobile-actions {
-  :deep(.el-button + .el-button) {
-    margin-left: 0 !important;
-  }
-
-  :deep(.el-button) {
-    box-sizing: border-box;
-    width: 100%;
-    min-width: 0;
-    max-width: 100%;
-  }
-}
+@use "@styles/custom/fa-login";
 </style>

frontend/web/src/components/views/fa-login/FaLoginQrPanel.vue

@@ -65,23 +65,5 @@ const qrPayload = computed(() => {
 </script>
 
 <style scoped lang="scss">
-@import "@styles/fa-login.css";
-
-.login-qr-flow {
-  margin-top: 1rem;
-}
-
-.login-qr-card {
-  box-sizing: border-box;
-}
-
-/* EP：相邻按钮横向间距；单列返回按钮无需处理 */
-.login-mobile-actions {
-  :deep(.el-button) {
-    box-sizing: border-box;
-    width: 100%;
-    min-width: 0;
-    max-width: 100%;
-  }
-}
+@use "@styles/custom/fa-login";
 </style>

frontend/web/src/components/views/fa-login/FaLoginRegisterPanel.vue

@@ -133,6 +133,6 @@ defineExpose({
 });
 </script>
 
-<style scoped>
-@import "@styles/fa-login.css";
+<style scoped lang="scss">
+@use "@styles/custom/fa-login";
 </style>