feat(auth): 后台登录、角色权限与会话访问策略

管理员与客服分角色登录，权限由后端判定；前端补齐登录、人员与组织管理页面。

frontend/src/components/layout/SidebarToggle.vue

@@ -0,0 +1,64 @@
+<!--
+Copyright 2024-2026 ReplyPier
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<script setup lang="ts">
+defineProps<{
+    isCollapsed: boolean
+}>()
+
+defineEmits<{
+    (e: 'toggle'): void
+}>()
+</script>
+
+<template>
+    <button class="toggle-btn" @click="$emit('toggle')">
+        <span class="toggle-icon">{{ isCollapsed ? '▶' : '◀' }}</span>
+    </button>
+</template>
+
+<style scoped>
+.toggle-btn {
+    width: 26px;
+    height: 26px;
+    flex-shrink: 0;
+    background: var(--o05);
+    border: 1px solid var(--o10);
+    border-radius: 7px;
+    color: var(--muted);
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    transition: background-color var(--transition-fast), color var(--transition-fast),
+        border-color var(--transition-fast), box-shadow var(--transition-fast);
+}
+
+.toggle-btn:hover {
+    background: var(--o10);
+    color: var(--text2);
+}
+
+.toggle-btn:focus-visible {
+    outline: none;
+    box-shadow: var(--ring-focus);
+}
+
+.toggle-icon {
+    font-size: 12px;
+    line-height: 1;
+}
+</style>