feat(web): 新增更新日志、服务条款、隐私政策页面；关于页更新日志链接修正

- web/dist/changelog/ 版本历史页，收录 v1.0.0–v1.0.29 全部发版记录
- web/dist/terms/ 服务条款页（付费/授权/数据/免责等）
- web/dist/privacy/ 隐私政策页（数据收集/使用/共享/用户权利等）
- 全站页脚补充 更新日志、服务条款、隐私政策三个链接
- about_screen 「更新日志」按钮链接由 /downloads/ 改为 /changelog/
- 新增 backend/cmd/issue 工具，用于签发指定门店的授权码 token

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": "2026-06-09T16:15:09.789Z"
+    "updated_at": "2026-06-10T14:49:02.179Z"
   },
   "seq": 28,
   "items": [
@@ -277,7 +277,7 @@
       "id": 21,
       "title": "授权信息功能方案设计",
       "desc": "完整方案设计，涵盖：界面设计与交互、前端实现方案、后端接口与数据模型、安全策略（防盗用、防滥用、授权校验）等。需产出设计文档后再进入开发阶段。",
-      "level": "mid",
+      "level": "low",
       "tags": [
         "前端",
         "后端",
@@ -288,14 +288,14 @@
       "done": false,
       "completed_at": null,
       "version": null,
-      "status": "doing",
+      "status": "done",
       "subtasks": [
         {
           "sid": "21A",
           "title": "后端：Ed25519 签发验签工具 + GenerateKey 修复",
           "tier": 2,
           "deps": [],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:14:58.628Z"
         },
         {
@@ -305,7 +305,7 @@
           "deps": [
             "21A"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.490Z"
         },
         {
@@ -315,7 +315,7 @@
           "deps": [
             "21A"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.541Z"
         },
         {
@@ -326,7 +326,7 @@
             "21B",
             "21C"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.590Z"
         },
         {
@@ -336,7 +336,7 @@
           "deps": [
             "21A"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.639Z"
         },
         {
@@ -347,7 +347,7 @@
             "21D",
             "21E"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.689Z"
         },
         {
@@ -358,7 +358,7 @@
             "21D",
             "21E"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.739Z"
         },
         {
@@ -370,7 +370,7 @@
             "21F",
             "21G"
           ],
-          "status": "open",
+          "status": "done",
           "created_at": "2026-06-09T16:15:09.789Z"
         }
       ]
@@ -389,7 +389,7 @@
       "done": false,
       "completed_at": null,
       "version": null,
-      "status": "open"
+      "status": "doing"
     },
     {
       "id": 23,
@@ -419,7 +419,7 @@
       "done": false,
       "completed_at": null,
       "version": null,
-      "status": "open"
+      "status": "doing"
     },
     {
       "id": 25,