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/server/routes/feedback/index.ts

@@ -54,6 +54,9 @@ const VALID_STATUS = new Set(['open', 'in_progress', 'done', 'rejected']);
 
 const VALID_TYPES = new Set(['dimension', 'bug', 'ux', 'other']);
 
+// 写入时间戳一律用东八区 CST，避免依赖 MySQL/容器时区设置
+const CST_NOW = `DATE_ADD(UTC_TIMESTAMP(), INTERVAL 8 HOUR)`;
+
 app.post('/submit', async (c) => {
   await ensureTable();
   const body = await c.req.json().catch(() => ({})) as {
@@ -79,7 +82,7 @@ app.post('/submit', async (c) => {
 
   const [r] = await pool.query<ResultSetHeader>(
     `INSERT INTO bi_user_feedback (type, module, content, contact, screenshots, user_id, user_name, user_agent, created_at)
-     VALUES (?, ?, ?, ?, ?, ?, ?, ?, NOW())`,
+     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ${CST_NOW})`,
     [type, moduleVal, content, contact, JSON.stringify(screenshots), user?.userId || null, user?.userName || null, userAgent],
   );
   return c.json({ ok: true, id: r.insertId });
@@ -174,7 +177,7 @@ app.patch('/:id', async (c) => {
   }
   if (typeof body.reply === 'string') {
     const reply = body.reply.trim().slice(0, 2000);
-    fields.push('reply_content = ?', 'reply_user = ?', 'reply_at = NOW()');
+    fields.push('reply_content = ?', 'reply_user = ?', `reply_at = ${CST_NOW}`);
     const user = (c as { get?: (k: string) => unknown }).get?.('user') as AuthUser | undefined;
     params.push(reply || null, user?.userName || user?.userId || null);
   }