feat(i18n): add saveFailed message and dimensionRatesMixedHint to locale files

- Updated English, Nepali, and Chinese locale files to include a new message for "Failed to save configuration".
- Added a hint for mixed rebate rates within the same dimension to enhance user understanding.
- Improved internationalization support across multiple locales for better user experience in the admin interface.

src/i18n/locales/en/config.json

@@ -63,7 +63,8 @@
     "refreshing": "Refreshing",
     "refresh": "Refresh versions",
     "newDraft": "New draft",
-    "saveDraft": "Save draft"
+    "saveDraft": "Save draft",
+    "saveFailed": "Failed to save configuration"
   },
   "wallet": {
     "title": "Wallet transfer limit settings",
@@ -318,6 +319,7 @@
     "deleteFailed": "Delete failed",
     "editingVersion": "Editing version v{{version}} · {{status}}",
     "readOnlyHint": "Create a draft before editing rebate.",
+    "dimensionRatesMixedHint": "Rebate rates within the same dimension (2D/3D/4D) are not identical: the three percentage inputs show the first play (alphabetically) that has the primary prize scope; use the table as the source of truth. Bulk inputs will overwrite all plays in that dimension to one rate.",
     "fields": {
       "d2": "2D rebate rate (%)",
       "d3": "3D rebate rate (%)",