fix: restore CSS file to correct location

- Move style.scss back to assets/css/ to fix Jekyll build path
- Remove backup file
- Keep Mermaid diagram format changes

This fixes the broken CSS on the live site while preserving
the Mermaid diagram improvements.

assets/css/style.scss.backup

@@ -1,145 +0,0 @@
----
----
-
-// Import settings in correct sequence
-:root {
-    --color-primary: #7fb100;
-    --color-secondary: #446200;
-    --color-text: #f2f3f2;
-    --color-text-muted: #aaa;
-    --color-background: #1c1d1b;
-    --color-border: #2d2e2c;
-    --color-code-background: #2a2b29;
-    --color-code-header-bg: #252624;
-    --dox-border-radius: 4px;
-    --font-family-code: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, Courier, monospace;
-}
-
-@import "settings/core";
-@import "settings/colors";
-@import "settings/layout";
-
-// Import tools
-@import "tools/breakpoints";
-@import "tools/grid";
-
-// Import generic
-@import "generic/box-sizing";
-@import "generic/normalize";
-@import "generic/reset";
-@import "generic/fonts";
-
-// Import elements
-@import "elements/page";
-@import "elements/headings";
-@import "elements/hr";
-@import "elements/links";
-@import "elements/lists";
-@import "elements/images";
-@import "elements/tables";
-@import "elements/code";
-@import "elements/forms";
-@import "elements/media";
-
-// Import objects
-@import "objects/grid";
-@import "objects/tables";
-@import "objects/icons";
-@import "objects/list-bare";
-@import "objects/list-inline";
-@import "objects/link-bare";
-
-// Import components
-@import "components/header";
-@import "components/logo";
-@import "components/navigation";
-@import "components/offcanvas";
-@import "components/hamburger-icon";
-@import "components/buttons";
-@import "components/hero";
-@import "components/footer";
-@import "components/post";
-@import "components/feature-card";
-@import "components/example";
-@import "components/callout";
-@import "components/arrow-link";
-@import "components/page-nav";
-@import "components/code";
-
-// Import utilities
-@import "utilities/backgrounds";
-@import "utilities/display";
-@import "utilities/flexbox";
-@import "utilities/grid";
-@import "utilities/headings";
-@import "utilities/positioning";
-@import "utilities/spacing";
-@import "utilities/typography";
-
-// Import vendors
-@import "vendors/code-highlight";
-
-// MainWP Dark Theme Customizations
-:root {
-  --mainwp-primary: #{$dox-color-primary};
-  --mainwp-primary-dark: #446200;
-  --mainwp-accent: #4682b4;
-  --mainwp-dark-bg: #1c1d1b;
-  --mainwp-dark-text: #f2f3f2;
-  --mainwp-warning: #ad0000;
-  --mainwp-highlight: #ffd300;
-}
-
-body {
-  background-color: var(--mainwp-dark-bg);
-  color: var(--mainwp-dark-text);
-}
-
-.c-header {
-  background-color: var(--mainwp-dark-bg);
-  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
-}
-
-.c-nav__link {
-  color: var(--mainwp-dark-text);
-  &:hover {
-    color: var(--mainwp-primary);
-  }
-}
-
-.c-footer {
-  background-color: var(--mainwp-dark-bg);
-  border-top: 1px solid rgba(255, 255, 255, 0.1);
-  color: var(--mainwp-dark-text);
-}
-
-a {
-  color: var(--mainwp-primary);
-  &:hover {
-    color: var(--mainwp-primary-dark);
-  }
-}
-
-.c-button {
-  background-color: var(--mainwp-primary);
-  &:hover {
-    background-color: var(--mainwp-primary-dark);
-  }
-}
-
-pre, code {
-  background-color: rgba(0, 0, 0, 0.2);
-  border: 1px solid rgba(255, 255, 255, 0.1);
-}
-
-.c-post {
-  background-color: rgba(0, 0, 0, 0.2);
-  border: 1px solid rgba(255, 255, 255, 0.1);
-}
-
-// Add Inter font
-@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');
-
-body {
-  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
-}