feat(nav): 侧栏高对比度 + 顶栏已打开页面标签 + 折叠态只留日夜切换 + 换明月图标

1) 侧边栏对比度
   - 新增 --sb-* 专属色板（固定深色底，不随日夜主题翻转），文字 #c3d7e3、
     hover 纯白、选中纯白 + 品牌色强调条 + 内描边，参考 GoodJob 的 Command Deck
   - 原过渡曲线（--transition-fast/base）保持不变
   - luxury.css 里把侧栏刷回浅底的覆盖一并改为同一套色板

2) 顶栏「已打开页面」标签
   - 新增 src/navigation.js：NAV_GROUPS 与 PAGE_LABELS 单点维护，App 与顶栏共用
   - GlobalHeader 用 useLocation 自动登记访问过的页面，工作台恒定置顶且不可关闭，
     其余按最近使用排序，可单独关闭，最多 10 个，落 localStorage（happy.openTabs）
   - 关掉当前标签会退到剩下的最近一个，没有则回工作台

3) 折叠态页脚
   - .sidebar.collapsed .settings-btn 隐藏，76px 宽度下只留一个日夜切换按钮

4) 明月图标
   - MoonIcon → MoonStarsIcon，造型取自 igoutu.cn/icon/101343/moon-and-stars，
     重绘为矢量（月牙 = 两段圆弧相减，两枚凹边圆角四角星），走 currentColor 随主题变色
   - 源图存 design-refs/（已忽略，不入库）

5) 顶栏排布修正
   - 标签条加入后头部变挤，收窄品牌区/搜索框，按钮加 nowrap 防止文字折行
   - ≤1280px 隐藏标签条

frontend/src/components/GlobalHeader.jsx

@@ -1,7 +1,20 @@
 import React, { useEffect, useMemo, useRef, useState } from 'react'
-import { useNavigate } from 'react-router-dom'
+import { useLocation, useNavigate } from 'react-router-dom'
 import axios from 'axios'
 import { BotIcon, ClockIcon, CloudDbIcon, PlusCircleIcon, SearchIcon } from './Icons'
+import { HOME_PATH, PAGE_LABELS } from '../navigation'
+
+const TABS_STORAGE_KEY = 'happy.openTabs'
+const MAX_TABS = 10
+
+/* 从本地缓存读取上次打开的页面（只保留仍然存在的路由，工作台恒定在首位） */
+function readStoredTabs() {
+  try {
+    const raw = JSON.parse(localStorage.getItem(TABS_STORAGE_KEY) || '[]')
+    const list = Array.isArray(raw) ? raw.filter(path => PAGE_LABELS[path]) : []
+    return [HOME_PATH, ...list.filter(path => path !== HOME_PATH)]
+  } catch { return [HOME_PATH] }
+}
 
 function GlobalHeader({ onOpenAssistant }) {
   const [now, setNow] = useState(new Date())
@@ -9,14 +22,44 @@ function GlobalHeader({ onOpenAssistant }) {
   const [query, setQuery] = useState('')
   const [results, setResults] = useState([])
   const [searching, setSearching] = useState(false)
+  const [openTabs, setOpenTabs] = useState(readStoredTabs)
   const searchRef = useRef(null)
+  const tabsRef = useRef(null)
   const navigate = useNavigate()
+  const location = useLocation()
 
   useEffect(() => {
     const timer = window.setInterval(() => setNow(new Date()), 1000)
     return () => window.clearInterval(timer)
   }, [])
 
+  /* 访问过的页面自动登记成标签：工作台恒在首位，其余按最近使用排序，新页插在第二位 */
+  useEffect(() => {
+    const path = location.pathname
+    if (!PAGE_LABELS[path]) return
+    setOpenTabs(current => {
+      if (current[0] === path) return current
+      if (current[1] === path) return current
+      const rest = current.filter(item => item !== path && item !== HOME_PATH)
+      return [HOME_PATH, path, ...rest].slice(0, MAX_TABS)
+    })
+  }, [location.pathname])
+
+  useEffect(() => {
+    try { localStorage.setItem(TABS_STORAGE_KEY, JSON.stringify(openTabs)) } catch { /* 存储不可用时仅本次会话有效 */ }
+    const active = tabsRef.current?.querySelector('.page-tab.active')
+    active?.scrollIntoView({ block: 'nearest', inline: 'nearest' })
+  }, [openTabs, location.pathname])
+
+  /* 关闭标签：关掉的若是当前页，就退到剩下的最近一个，没有则回工作台 */
+  const closeTab = (event, path) => {
+    event.stopPropagation()
+    const next = openTabs.filter(item => item !== path)
+    const result = next.length ? next : [HOME_PATH]
+    setOpenTabs(result)
+    if (path === location.pathname) navigate(result[0])
+  }
+
   useEffect(() => {
     const keyword = query.trim()
     if (!keyword) { setResults([]); setSearching(false); return }
@@ -59,6 +102,20 @@ function GlobalHeader({ onOpenAssistant }) {
           <div className="global-search-footnote">已检索客户、供应商、产品、订单、商机、待办和活动记录</div>
         </div>}
       </div>
+      {/* 已打开页面：搜索框后的快速跳转标签，工作台常驻且不可关闭 */}
+      <nav className="page-tabs" ref={tabsRef} aria-label="已打开页面">
+        {openTabs.map(path => {
+          const label = PAGE_LABELS[path] || path
+          const isHome = path === HOME_PATH
+          const active = location.pathname === path
+          return (
+            <div key={path} className={`page-tab${active ? ' active' : ''}`}>
+              <button type="button" className="page-tab-label" title={label} aria-current={active ? 'page' : undefined} onClick={() => navigate(path)}>{label}</button>
+              {!isHome && <button type="button" className="page-tab-close" aria-label={`关闭${label}`} title={`关闭${label}`} onClick={event => closeTab(event, path)}>×</button>}
+            </div>
+          )
+        })}
+      </nav>
       <div className="global-header-actions"><div className="header-clock"><ClockIcon size={16} /><span>{dateLabel}</span><b>{timeLabel}</b></div><button className="quick-create-btn" title="快速新建"><PlusCircleIcon size={19} /><span>快速新建</span></button><button className="ai-entry-btn" onClick={onOpenAssistant} title="打开 AI 助手"><BotIcon size={19} /><span>AI 助手</span><i>β</i></button><button className="header-avatar" title="当前用户">W</button><button className="mobile-search-btn" onClick={() => { setSearchOpen(v => !v); window.setTimeout(() => searchRef.current?.focus(), 0) }} title="搜索"><SearchIcon size={18} /></button></div>
     </header>
   )