refactor: remove single-use notification constant

- Replace constant usage with direct message string in ImportDerivedAccountView.vue
- Clean up import statement to remove unused import
- Remove unused constant from notifications.ts

src/constants/notifications.ts

@@ -1697,11 +1697,3 @@ export const NOTIFY_DUPLICATE_ACCOUNT_IMPORT = {
   message:
     "This account has already been imported. Please use a different seed phrase or check your existing accounts.",
 };
-
-// ImportDerivedAccountView.vue specific constants
-// Used in: ImportDerivedAccountView.vue (incrementDerivation method - duplicate derived account warning)
-export const NOTIFY_DUPLICATE_DERIVED_ACCOUNT = {
-  title: "Derived Account Already Exists",
-  message:
-    "This derived account already exists. Please try a different derivation path.",
-};