delete margin (#7904)

Ref: #4493

Before:
<img width="816" height="571" alt="grafik" src="https://github.com/user-attachments/assets/bfc6c933-5e4e-46e8-91d7-0e0e7b469671" />

After:
<img width="795" height="523" alt="grafik" src="https://github.com/user-attachments/assets/5b5a668c-c3ca-46ef-be69-ad5b5b90a412" />

p/themes/base-theme/base.css

@@ -466,7 +466,6 @@ th {
 }
 
 .prompt input {
-	margin: 5px auto;
 	width: 100%;
 }
 

p/themes/base-theme/base.rtl.css

@@ -466,7 +466,6 @@ th {
 }
 
 .prompt input {
-	margin: 5px auto;
 	width: 100%;
 }
 

p/themes/base-theme/frss.css

@@ -354,7 +354,6 @@ textarea:invalid {
 .prompt input,
 .prompt select,
 .prompt .stick {
-	margin: 5px auto;
 	width: 100%;
 	box-sizing: border-box;
 }

p/themes/base-theme/frss.rtl.css

@@ -354,7 +354,6 @@ textarea:invalid {
 .prompt input,
 .prompt select,
 .prompt .stick {
-	margin: 5px auto;
 	width: 100%;
 	box-sizing: border-box;
 }