fix(backend): 架构质量改进批次二 (#32-37)

- #32 License 激活迁移到 license_devices 表：Activate/Verify/Deactivate 全部改用
  license_devices，新增 max_devices 校验和 GET /license/devices 端点；
  Activate 现在校验 shop_id 防跨租户激活
- #33 checkInventory 从 StockOutHandler 移到 StockService.CheckInventoryAvailability
- #34 新增 util/response.go 统一错误响应工具（RespondError/RespondSuccess/RespondCreated）
- #35 生产模式 CORS Origin='*' 启动时 Fatal
- #36 生产模式 License 私钥未配置启动时 Fatal
- #37 新增 util/page.go ValidatePageSize，应用到 partner/product/stock_in/stock_out handler

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

todo/todo.json

@@ -1,7 +1,7 @@
 {
   "meta": {
     "title": "酒库管理系统 — 项目 TODO",
-    "updated_at": "2026-06-10T15:32:03.641Z"
+    "updated_at": "2026-06-10T16:38:37.763Z"
   },
   "seq": 40,
   "items": [
@@ -477,7 +477,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:13.249Z",
       "done": false,
       "completed_at": null,
@@ -492,7 +492,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:15.102Z",
       "done": false,
       "completed_at": null,
@@ -507,7 +507,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:16.854Z",
       "done": false,
       "completed_at": null,
@@ -523,7 +523,7 @@
         "后端",
         "数据库"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:25.715Z",
       "done": false,
       "completed_at": null,
@@ -538,7 +538,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:28.106Z",
       "done": false,
       "completed_at": null,
@@ -553,7 +553,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:33.596Z",
       "done": false,
       "completed_at": null,
@@ -568,7 +568,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:44.159Z",
       "done": false,
       "completed_at": null,
@@ -583,7 +583,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:46.792Z",
       "done": false,
       "completed_at": null,
@@ -598,7 +598,7 @@
       "tags": [
         "后端"
       ],
-      "status": "open",
+      "status": "done",
       "created_at": "2026-06-10T15:31:49.032Z",
       "done": false,
       "completed_at": null,