fix(clients): reject spaces, '/', '\' and control chars in subscription ID

Like the client email, the subId is embedded directly in subscription
URLs, so the same characters break it. Validate it on the backend
(Create + Update) and the frontend (Zod), with a localized message
across all 13 locales. An empty subId stays allowed (it is then
auto-generated).

web/translation/zh-TW.json

@@ -647,6 +647,7 @@
       "online": "上線",
       "email": "電子郵件",
       "emailInvalidChars": "電子郵件不能包含空格、'/'、'\\' 或控制字元",
+      "subIdInvalidChars": "訂閱ID不能包含空格、'/'、'\\' 或控制字元",
       "group": "群組",
       "groupDesc": "用於將相關客戶端歸類的邏輯標籤(如團隊、客戶、地區)。可從工具列篩選。",
       "groupPlaceholder": "如 customer-a",