chore(frontend): upgrade Bootswatch and Bootstrap SCSS to v5.3.3

- Upgraded Bootswatch SCSS source files across all 25 themes (dev/scss/bootswatch/) to v5.3.3
- Upgraded Bootstrap SCSS source files (dev/scss/bootstrap/) to v5.3.3 to match static/js/bootstrap.bundle.min.js
- Updated dev/scss/bootstrap-overrides.scss to import bootstrap/variables-dark
- Verified error-free LibSass compilation for all 26 themes (25 Bootswatch + bootstrap-orj)
- Recompiled static/css/wvc-main.min.css

dev/scss/bootswatch/simplex/_bootswatch.scss

@@ -1,4 +1,4 @@
-// Simplex 5.2.2
+// Simplex 5.3.3
 // Bootswatch
 
 
@@ -6,11 +6,7 @@
 
 $web-font-path: "https://fonts.googleapis.com/css2?family=Open+Sans:wght@400;700&display=swap" !default;
 @if $web-font-path {
-  @import url($web-font-path);
-}
-
-:root {
-  color-scheme: light;
+  @import url("#{$web-font-path}");
 }
 
 // Mixins
@@ -37,7 +33,6 @@ $web-font-path: "https://fonts.googleapis.com/css2?family=Open+Sans:wght@400;700
   }
 
   &.bg-primary {
-    background-color: $primary !important;
     border-color: shade-color($primary, 13%) !important;
   }
 

dev/scss/bootswatch/simplex/_variables.scss

@@ -1,4 +1,4 @@
-// Simplex 5.2.2
+// Simplex 5.3.3
 // Bootswatch
 
 $theme: "simplex" !default;
@@ -63,9 +63,6 @@ $nav-tabs-border-color:             darken(#fff, 6.5%) !default;
 
 // Navbar
 
-$navbar-dark-color:                 rgba($white, .75) !default;
-$navbar-dark-hover-color:           $white !default;
-
 // Pagination
 
 $pagination-border-color:           $nav-tabs-border-color !default;