Normalize and improve font sizes

This commit standardizes font sizes across components for a uniform
look. The icon sizes, font weights and line heights are also adjusted
accordingly for better standardization and simplicity.

- Introduce variables for standard font sizes, enhancing
  maintainability.
- Remove explicit pixel values, replaced with scalable units based on
  root size.
- Remove workaround for line-height adoptation of bigger font-size.
- Use consistent small font-size for the code area.
- Adjust checkbox tick to scale with font size.

src/presentation/components/Code/CodeButtons/IconButton.vue

@@ -81,7 +81,7 @@ export default defineComponent({
   border-radius: 4px;
 
   .button__icon {
-    font-size: 2em;
+    font-size: $font-size-larger;
   }
 
   @include clickable;
@@ -99,10 +99,9 @@ export default defineComponent({
   .button__text {
     display: none;
     font-family: $font-artistic;
-    font-size: 1.5em;
+    font-size: $font-size-large;
     color: $color-primary;
     font-weight: 500;
-    line-height: 1.1;
     @include hover-or-touch {
       display: block;
     }

src/presentation/components/Code/CodeButtons/Save/RunInstructions/Steps/CopyableCommand.vue

@@ -63,14 +63,14 @@ export default defineComponent({
   padding: 0.2rem;
   .dollar {
     margin-right: 0.5rem;
-    font-size: 0.8rem;
+    font-size: $font-size-smaller;
     user-select: none;
   }
   .copy-action-container {
     margin-left: 1rem;
   }
   code {
-    font-size: 1rem;
+    font-size: $font-size-small;
   }
 }
 </style>