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/lux/_bootswatch.scss

@@ -1,16 +1,12 @@
-// Lux 5.2.2
+// Lux 5.3.3
 // Bootswatch
 
 
 // Variables
 
-$web-font-path: "https://fonts.googleapis.com/css2?family=Nunito+Sans:wght@400;600&display=swap" !default;
+$web-font-path: "https://fonts.googleapis.com/css2?family=Nunito+Sans:wght@200;300;400;500;600;700&display=swap" !default;
 @if $web-font-path {
-  @import url($web-font-path);
-}
-
-:root {
-  color-scheme: light;
+  @import url("#{$web-font-path}");
 }
 
 // Navbar
@@ -93,10 +89,15 @@ $web-font-path: "https://fonts.googleapis.com/css2?family=Nunito+Sans:wght@400;6
   border: 1px solid $gray-400 !important;
 }
 
+@include color-mode(dark) {
+  .btn-primary {
+    background-color: #080808;
+  }
+}
+
 // Typography
 
 body {
-  font-weight: 200;
   letter-spacing: 1px;
 }
 
@@ -135,6 +136,53 @@ th {
   }
 }
 
+// Forms
+
+@include color-mode(dark) {
+  .form-control {
+    color: $body-color;
+
+    &::placeholder {
+      color: $body-secondary-color;
+    }
+  }
+
+  .form-floating {
+    > label,
+    > .form-control:focus ~ label,
+    > .form-control:not(:placeholder-shown) ~ label,
+    > .form-control-plaintext ~ label,
+    > .form-select ~ label {
+      color: $body-secondary-color;
+    }
+
+    > .form-control::placeholder,
+    > .form-control-plaintext::placeholder {
+      color: transparent;
+    }
+  }
+
+  .form-check-input:checked {
+    background-color: $body-secondary-color;
+  }
+
+  .form-switch .form-check-input {
+    background-image: $form-switch-bg-image;
+  }
+
+  .form-range::-webkit-slider-thumb {
+    background-color: $gray-600;
+  }
+
+  .form-range:disabled::-webkit-slider-thumb {
+    background-color: $gray-800;
+  }
+
+  .input-group-text {
+    color: $body-secondary-color;
+  }
+}
+
 // Navs
 
 .dropdown-menu {

dev/scss/bootswatch/lux/_variables.scss

@@ -1,4 +1,4 @@
-// Lux 5.2.2
+// Lux 5.3.3
 // Bootswatch
 
 $theme: "lux" !default;
@@ -53,6 +53,15 @@ $body-color:                $gray-700 !default;
 
 // stylelint-disable-next-line value-keyword-case
 $font-family-sans-serif:      "Nunito Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol" !default;
+
+$font-weight-lighter:         lighter !default;
+$font-weight-light:           200 !default;
+$font-weight-normal:          300 !default;
+$font-weight-medium:          400 !default;
+$font-weight-semibold:        500 !default;
+$font-weight-bold:            600 !default;
+$font-weight-bolder:          bolder !default;
+
 $h1-font-size:                2rem !default;
 $h2-font-size:                1.75rem !default;
 $h3-font-size:                1.5rem !default;
@@ -88,6 +97,9 @@ $input-bg:                              $gray-200 !default;
 $input-disabled-bg:                     $gray-300 !default;
 $input-group-addon-bg:                  $gray-300 !default;
 
+$form-select-disabled-color:        $gray-600 !default;
+$form-select-disabled-bg:           $input-disabled-bg !default;
+
 // Navbar
 
 $navbar-padding-y:                  1.5rem !default;