fix(clients): reject spaces, '/', '\' and control chars in client email

Client emails containing a slash broke the path-param routes
(edit/delete/view returned 404 / "client not found"), leaving stale
records that could only be cleared with manual SQLite edits. Validate
the email on both the backend (Create + Update, which also covers the
bulk paths) and the frontend (Zod) so these characters are rejected at
save time with a clear, localized message across all 13 locales.

Closes #4695

web/translation/fa-IR.json

@@ -646,6 +646,7 @@
       "subId": "شناسه اشتراک",
       "online": "آنلاین",
       "email": "ایمیل",
+      "emailInvalidChars": "ایمیل نمی‌تواند شامل فاصله، '/'، '\\' یا کاراکترهای کنترلی باشد",
       "group": "گروه",
       "groupDesc": "برچسبی منطقی برای دسته‌بندی کاربران مرتبط (مثل تیم، مشتری، منطقه). از نوار ابزار قابل فیلتر است.",
       "groupPlaceholder": "مثلاً customer-a",