fix: light mode link/primary colors unreadable on white background (#10457)

Gold #FFD700 has 1.4:1 contrast ratio on white — barely visible.
Replace with dark amber palette (#8B6508 primary, #7A5800 links)
that passes WCAG AA (5.3:1 and 6.5:1 respectively).

Changes:
- :root primary palette → dark amber tones for light mode
- Explicit light mode link colors (#7A5800 / #5A4100 hover)
- Light mode sidebar active state with amber accent
- Light mode table header/border styling
- Footer hover color split by theme (gold for dark, amber for light)

Dark mode is completely unchanged.

Reported by @AbrahamMat7632

website/src/css/custom.css

@@ -8,20 +8,24 @@
 @import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap');
 
 :root {
-  /* Gold/Amber palette from landing page */
+  /* Dark amber palette for light mode — readable on white (WCAG AA compliant)
-  --ifm-color-primary: #FFD700;
+     Current gold #FFD700 has only 1.4:1 contrast on white; these tones pass 4.5:1+ */
-  --ifm-color-primary-dark: #E6C200;
+  --ifm-color-primary: #8B6508;
-  --ifm-color-primary-darker: #D9B700;
+  --ifm-color-primary-dark: #7A5800;
-  --ifm-color-primary-darkest: #B39600;
+  --ifm-color-primary-darker: #6E4F00;
-  --ifm-color-primary-light: #FFDD33;
+  --ifm-color-primary-darkest: #5A4100;
-  --ifm-color-primary-lighter: #FFE14D;
+  --ifm-color-primary-light: #9E7410;
-  --ifm-color-primary-lightest: #FFEB80;
+  --ifm-color-primary-lighter: #B38319;
+  --ifm-color-primary-lightest: #C89222;
 
   --ifm-font-family-base: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
   --ifm-font-family-monospace: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
 
   --ifm-code-font-size: 90%;
   --ifm-heading-font-weight: 600;
+
+  --ifm-link-color: #7A5800;
+  --ifm-link-hover-color: #5A4100;
 }
 
 /* Dark mode — the PRIMARY mode, matches landing page */
@@ -91,6 +95,13 @@
   padding-left: calc(var(--ifm-menu-link-padding-horizontal) - 3px);
 }
 
+/* Light mode sidebar active */
+[data-theme='light'] .menu__link--active:not(.menu__link--sublist) {
+  background-color: rgba(139, 101, 8, 0.08);
+  border-left: 3px solid #8B6508;
+  padding-left: calc(var(--ifm-menu-link-padding-horizontal) - 3px);
+}
+
 /* Code blocks */
 [data-theme='dark'] .prism-code {
   background-color: #0a0a12 !important;
@@ -167,6 +178,16 @@ pre.prism-code.language-ascii code {
   border-color: rgba(255, 215, 0, 0.06);
 }
 
+/* Light mode table styling */
+[data-theme='light'] table th {
+  background-color: rgba(139, 101, 8, 0.06);
+  border-color: rgba(139, 101, 8, 0.15);
+}
+
+[data-theme='light'] table td {
+  border-color: rgba(139, 101, 8, 0.10);
+}
+
 /* Footer */
 .footer {
   border-top: 1px solid rgba(255, 215, 0, 0.08);
@@ -177,11 +198,16 @@ pre.prism-code.language-ascii code {
   transition: color 0.2s;
 }
 
-.footer a:hover {
+[data-theme='dark'] .footer a:hover {
   color: #FFD700;
   text-decoration: none;
 }
 
+[data-theme='light'] .footer a:hover {
+  color: #7A5800;
+  text-decoration: none;
+}
+
 /* Scrollbar */
 [data-theme='dark'] ::-webkit-scrollbar {
   width: 8px;