fix(feedback): 隐藏页加返回按钮 + 入库时间用东八区

- FeedbackAdminPage / EleImportPage 头部加 ← 返回按钮：
  优先 history.back（来自 SPA 内跳转），否则 hash=#mileage 兜底回主页
- 反馈入库（created_at / reply_at）改为 DATE_ADD(UTC_TIMESTAMP, INTERVAL 8 HOUR)
  不再依赖 MySQL/容器的本地时区设置，固定 CST

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/modules/admin/FeedbackAdminPage.tsx

@@ -1,6 +1,6 @@
 import { useCallback, useEffect, useState } from 'react';
 import { motion, AnimatePresence } from 'motion/react';
-import { Inbox, RotateCcw, X, Send, CheckCircle2, AlertCircle, Image as ImageIcon, Loader2 } from 'lucide-react';
+import { Inbox, RotateCcw, X, Send, CheckCircle2, AlertCircle, Image as ImageIcon, Loader2, ArrowLeft } from 'lucide-react';
 import { fetchJson } from '../../auth/api-client';
 
 interface FeedbackItem {
@@ -129,16 +129,27 @@ export default function FeedbackAdminPage() {
     <div className="min-h-screen bg-[#F8F9FB] p-4 md:p-8">
       <div className="max-w-5xl mx-auto space-y-4">
         <header className="flex items-center justify-between">
-          <div className="flex items-center gap-3">
-            <div className="w-10 h-10 rounded-xl bg-gradient-to-br from-blue-500 to-cyan-400 flex items-center justify-center">
+          <div className="flex items-center gap-3 min-w-0">
+            <button
+              onClick={() => {
+                // 优先 history.back（来自 SPA 内部跳转）；否则回到主页
+                if (window.history.length > 1) window.history.back();
+                else { window.location.hash = '#mileage'; }
+              }}
+              className="w-9 h-9 rounded-xl bg-white border border-slate-100 hover:border-blue-200 hover:bg-blue-50 hover:text-blue-600 text-slate-500 flex items-center justify-center transition-colors flex-shrink-0"
+              title="返回"
+            >
+              <ArrowLeft size={16} />
+            </button>
+            <div className="w-10 h-10 rounded-xl bg-gradient-to-br from-blue-500 to-cyan-400 flex items-center justify-center flex-shrink-0">
               <Inbox size={18} className="text-white" />
             </div>
-            <div>
+            <div className="min-w-0">
               <h1 className="text-lg font-black text-slate-900 leading-tight">用户反馈管理</h1>
               <p className="text-[11px] font-bold text-slate-400">查看、回复、跟进用户提交的建议</p>
             </div>
           </div>
-          <button onClick={reload} className="p-2 text-slate-400 hover:text-blue-500" title="刷新">
+          <button onClick={reload} className="p-2 text-slate-400 hover:text-blue-500 flex-shrink-0" title="刷新">
             <RotateCcw size={16} className={loading ? 'animate-spin' : ''} />
           </button>
         </header>