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/flatly/_bootswatch.scss

@@ -1,4 +1,4 @@
-// Flatly 5.2.2
+// Flatly 5.3.3
 // Bootswatch
 
 
@@ -6,37 +6,11 @@
 
 $web-font-path: "https://fonts.googleapis.com/css2?family=Lato:ital,wght@0,400;0,700;1,400&display=swap" !default;
 @if $web-font-path {
-  @import url($web-font-path);
-}
-
-:root {
-  color-scheme: light;
-}
-
-// Navbar
-
-.bg-primary {
-  .navbar-nav .show > .nav-link,
-  .navbar-nav .nav-link.active,
-  .navbar-nav .nav-link:hover,
-  .navbar-nav .nav-link:focus {
-    color: $success !important;
-  }
+  @import url("#{$web-font-path}");
 }
 
 // Navs
 
-.nav-tabs {
-  .nav-link.active,
-  .nav-link.active:focus,
-  .nav-link.active:hover,
-  .nav-item.open .nav-link,
-  .nav-item.open .nav-link:focus,
-  .nav-item.open .nav-link:hover {
-    color: $primary;
-  }
-}
-
 .pagination {
   a:hover {
     text-decoration: none;