custom amount ui prettier (#4556)

## Description:

fixed font, 
sizing, 
back box wrapping, 
remove "buy for" 
centre the text by removing the ^ v arrows

before:
<img width="939" height="491" alt="image"
src="https://github.com/user-attachments/assets/3c747341-5238-47e8-b455-ea5827669e75"
/>



after:
<img width="936" height="746" alt="image"
src="https://github.com/user-attachments/assets/4b64f34b-98e4-4519-85bd-1f5c2799babd"
/>

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory

## Please put your Discord username so you can be contacted if a bug or
regression is found:

w.o.n

src/client/styles.css

@@ -58,6 +58,17 @@
     color: var(--color-gray-400);
   }
 
+  .custom-plutonium-input {
+    appearance: textfield;
+    -moz-appearance: textfield;
+  }
+
+  .custom-plutonium-input::-webkit-outer-spin-button,
+  .custom-plutonium-input::-webkit-inner-spin-button {
+    -webkit-appearance: none;
+    margin: 0;
+  }
+
   button:not(:disabled),
   [role="button"]:not(:disabled) {
     cursor: pointer;