feat: add user-frontend i18n keys for new nav structure

Add home, customers, biz, agent i18n keys to zh-CN and en locale files

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

user-frontend/src/locales/en.json

@@ -1,22 +1,23 @@
 {
   "nav": {
-    "home": "Workspace",
+    "home": "Home",
     "more": "More",
-    "productsQuotations": "Products & Quotes",
-    "discovery": "Find Buyers",
     "workspace": "Dashboard",
     "customers": "Customers",
-    "products": "Products",
+    "biz": "Business",
-    "quotations": "Quotations",
-    "translate": "Translate",
-    "marketing": "Marketing",
-    "followup": "Follow-ups",
     "analytics": "Analytics",
     "team": "Team",
     "notifications": "Notifications",
     "profile": "Profile",
     "credits": "Buy Credits",
-    "settings": "Settings"
+    "settings": "Settings",
+    "customerList": "Customers",
+    "discovery": "Find Buyers",
+    "followup": "Follow-ups",
+    "translate": "Translate",
+    "products": "Products",
+    "quotations": "Quotations",
+    "marketing": "Marketing"
   },
   "topbar": {
     "credits": "credits",

user-frontend/src/locales/zh-CN.json

@@ -1,22 +1,23 @@
 {
   "nav": {
-    "home": "首页工作台",
+    "home": "首页",
     "more": "更多",
-    "productsQuotations": "报价产品",
-    "discovery": "发现客户",
     "workspace": "工作台",
-    "customers": "客户管理",
+    "customers": "客户工作台",
-    "products": "产品库",
+    "biz": "业务工作台",
-    "quotations": "报价单",
-    "translate": "智能翻译",
-    "marketing": "营销素材",
-    "followup": "跟进提醒",
     "analytics": "数据分析",
     "team": "团队协作",
     "notifications": "通知中心",
     "profile": "个人中心",
     "credits": "购买次数",
-    "settings": "设置"
+    "settings": "设置",
+    "customerList": "客户列表",
+    "discovery": "发现客户",
+    "followup": "跟进提醒",
+    "translate": "智能翻译",
+    "products": "产品库",
+    "quotations": "报价单",
+    "marketing": "营销素材"
   },
   "topbar": {
     "credits": "次",