Override Bootstrap dropdown CSS variables completely: no borders, no radius, no shadow, auto-width

- Set --bs-dropdown-min-width: 0 (width adapts to content)
- Set --bs-dropdown-border-width: 0 (no borders)
- Set --bs-dropdown-border-radius: 0 (no rounded corners)
- Set --bs-dropdown-box-shadow: none (no shadow)
- Set --bs-dropdown-padding-x/y: 0 (no padding)
- white-space: nowrap and width: auto on dropdown-item
- Same overrides on submenu dropdown-menu

themes/default/assets/css/theme.css

@@ -69,18 +69,26 @@
 }
 
 .dropdown-menu {
+  --bs-dropdown-min-width: 0;
+  --bs-dropdown-padding-x: 0;
+  --bs-dropdown-padding-y: 0;
+  --bs-dropdown-border-width: 0;
+  --bs-dropdown-border-radius: 0;
+  --bs-dropdown-box-shadow: none;
   background-color: var(--header-bg) !important;
   border: none !important;
   border-radius: 0 !important;
   padding: 0 !important;
   margin: 0 !important;
   min-width: 0 !important;
+  box-shadow: none !important;
 }
 .dropdown-item {
   color: var(--header-font) !important;
   border-radius: 0 !important;
-  padding: 0.5rem 1rem;
+  padding: 0.4rem 1rem;
   white-space: nowrap;
+  width: auto;
 }
 .dropdown-item:hover, .dropdown-item:focus {
   background-color: rgba(255, 255, 255, 0.1) !important;
@@ -310,8 +318,12 @@ pre code {
   margin-top: 0;
   margin-left: 0;
   display: none;
+  --bs-dropdown-border-width: 0;
+  --bs-dropdown-border-radius: 0;
+  --bs-dropdown-box-shadow: none;
   border: none !important;
   border-radius: 0 !important;
+  box-shadow: none !important;
 }
 .dropdown-submenu:hover > .dropdown-menu {
   display: block;