feat(sub): per-inbound sort order for subscription links

Add a subSortIndex field to inbounds that controls the order of links
in subscription output only: the raw sub body, the HTML sub page, and
the JSON/Clash formats (all served from the same query). Lower values
come first; ties keep id order. The panel inbound list is unaffected.

The value is editable in the inbound form next to the share-address
fields, propagates to nodes via wireInbound, and follows the usual
node-sync rules (copied on import, mirrored while not dirty, never a
structural change).

Rescoped from #5214 by @Ponywka.

internal/web/translation/zh-CN.json

@@ -416,6 +416,7 @@
       },
       "telegramDesc": "请提供Telegram聊天ID。（在机器人中使用'/id'命令）或（{'@'}userinfobot",
       "subscriptionDesc": "要找到你的订阅 URL，请导航到“详细信息”。此外，你可以为多个客户端使用相同的名称。",
+      "subSortIndex": "订阅排序",
       "same": "相同",
       "inboundInfo": "入站信息",
       "exportInbound": "导出入站规则",
@@ -595,6 +596,8 @@
         "shareAddrStrategyHelp": "控制导出分享链接、二维码和订阅输出时写入哪个地址。",
         "shareAddr": "自定义分享地址",
         "shareAddrHelp": "仅在分享地址策略为自定义时使用。填写不带协议和端口的域名或 IP。",
+        "subSortIndex": "订阅排序",
+        "subSortIndexHelp": "此入站的链接在订阅输出（订阅页面和客户端应用）中的位置。数值越小越靠前；数值相同时保持创建顺序。不影响面板中的入站列表。",
         "shareAddrStrategyOptions": {
           "node": "节点地址",
           "listen": "入站监听地址",