fix: add feedback after successfully adding a user in admin panel (#1462)

## Summary
- Show success toast notification after user is added
- Refresh user list and navigate to 'normal' filter on page 1 to display
the newly added user

## Problem
When adding a user in Admin -> Users, the page had no feedback after
submission (as reported in #1457).

**Root cause:** The code only refreshed the user list if the current
filter was "all" or "staff", but the default filter is "normal".
Additionally, there was no success toast notification.

## Solution
1. Added toast notification to confirm successful user creation
2. After adding user, navigate to "normal" filter page 1 and refresh the
list so the new user is visible

## Test plan
1. Go to Admin -> Users
2. Click "Add User"
3. Submit user information
4. ✅ Success toast should appear
5. ✅ Page should navigate to "normal" filter
6. ✅ Newly added user should be visible in the list

Fixes #1457

---------

Co-authored-by: LinkinStars <linkinstar@foxmail.com>

Author: bimakw

i18n/en_US.yaml

@@ -2383,6 +2383,7 @@ ui:
     user_normal: This user is already normal.
     user_suspended: This user has been suspended.
     user_deleted: This user has been deleted.
+    user_added: User has been added successfully.
     badge_activated: This badge has been activated.
     badge_inactivated: This badge has been inactivated.
     users_deleted: These users have been deleted.

ui/src/pages/Admin/Users/index.tsx

@@ -109,9 +109,14 @@ const Users: FC = () => {
       return new Promise((resolve, reject) => {
         addUsers(userModel)
           .then(() => {
-            if (/all|staff/.test(curFilter) && curPage === 1) {
-              refreshUsers();
-            }
+            toastStore.getState().show({
+              msg: t('user_added', { keyPrefix: 'messages' }),
+              variant: 'success',
+            });
+            urlSearchParams.set('filter', 'normal');
+            urlSearchParams.delete('page');
+            setUrlSearchParams(urlSearchParams);
+            refreshUsers();
             resolve(true);
           })
           .catch((e) => {

ui/src/pages/SideNavLayout/index.tsx

@@ -38,7 +38,7 @@ const Index: FC = () => {
             <Outlet />
           </div>
         </div>
-        <div className="d-flex justify-content-center">
+        <div className="d-flex justify-content-center px-0 px-md-4">
           <div className="main-mx-with">
             <Footer />
           </div>