Move curriculum-nav to before-header-panel to avoid positioning hacks

Previously it was being rendered as a button on the right hand side of the header, and then `position:fixed` was used to pull it to the left. This made for some weird rendering quirks. This commit uses a plugin outlet to render it in the correct part of the HTML, which removes the need for the positioning workarounds.

common/common.scss

@@ -230,7 +230,7 @@ p.footer-donation {
   padding: 5px 10px;
 }
 
-@include at-least(screen-sm-min){
+@include at-least(screen-sm-min) {
   .trending-guides-row {
     display: flex;
     flex-direction: row;
@@ -443,12 +443,8 @@ body.no-ember {
 }
 
 a.curriculum-nav {
-  z-index: 1000;
   color: white;
-  position: fixed;
   padding: 0 10px;
-  left: 15px;
-  margin-top: -19px;
   height: $--global-nav-height;
   display: flex;
   align-items: center;
@@ -827,7 +823,7 @@ div.select-kit-header {
   margin-top: calc(-1rem - #{$--global-nav-height} * 2);
 }
 
-@include at-least(screen-md-min) { 
+@include at-least(screen-md-min) {
   .anchor {
     padding-top: calc(#{$--global-nav-height} + 1rem);
     margin-top: calc(-1rem - #{$--global-nav-height});

javascripts/discourse/api-initializers/freecodecamp.gjs

@@ -6,7 +6,7 @@ export default apiInitializer("0.8", (api) => {
     ? settings.curriculum_title_short
     : settings.curriculum_title;
 
-  api.headerButtons.add("curriculum-nav", <template>
+  api.renderInOutlet("before-header-panel", <template>
     <a class="curriculum-nav" href={{settings.curriculum_src}}>{{rawLabel}}</a>
   </template>);