feat: 落地页改造 + 集章弹窗全状态品牌/奖品说明

- 落地页：顶部改为活动海报，底部替换为「活动规则」5 条编号列表
- 集章收集弹窗 (StampPopup)：新增奖品规则卡片展示 Prize 信息
- 集章册 (AlbumPage / StampGrid)：所有状态图章均可点击查看详情
- 兑换弹窗 (RedeemModal)：新增 uncollected 分支，统一承载未收集/
  已集齐/已兑换三种状态；新增可选品牌说明区
- 后端 /api/stamps/:id 补充返回 prize 字段
- 管理后台字段标签改名：备注 → 品牌说明；奖品描述 → 奖品说明
- 新增一次性脚本 update-brand-rules，批量写入 16 条品牌权益文案

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

packages/server/src/routes/stamps.ts

@@ -54,7 +54,10 @@ router.get("/", optionalAuth, async (req, res) => {
 });
 
 router.get("/:id", async (req, res) => {
-  const stamp = await prisma.stamp.findUnique({ where: { id: req.params.id } });
+  const stamp = await prisma.stamp.findUnique({
+    where: { id: req.params.id },
+    include: { prize: true },
+  });
   if (!stamp) {
     res.status(404).json({ success: false, error: { code: "NOT_FOUND", message: "图章不存在" } });
     return;
@@ -68,6 +71,15 @@ router.get("/:id", async (req, res) => {
       imageColor: stamp.imageColor,
       imageGrey: stamp.imageGrey,
       sortOrder: stamp.sortOrder,
+      prize: stamp.prize
+        ? {
+            id: stamp.prize.id,
+            name: stamp.prize.name,
+            description: stamp.prize.description,
+            stock: stamp.prize.stock,
+            enabled: stamp.prize.enabled,
+          }
+        : null,
     },
   });
 });