v3 UI: Fix dark mode visual bugs (NK-pbqvke)

- Sidebar uses grey background with dark text in dark mode
- Sidebar toggle has no background in dark mode
- Sidebar search input uses light bg with dark text in dark mode
- item-description links use correct color (--link-color = #5ac8fa in dark)
  and no underline (fixed in prior commit)

https://claude.ai/code/session_01DpWhB9uGGMBnzqS28HxnuV

1 files changed, 33 insertions, 0 deletions

diff --git a/frontend-vanilla/src/style.css b/frontend-vanilla/src/style.css
index 0a2d0f3..7180d43 100644
--- a/frontend-vanilla/src/style.css
+++ b/frontend-vanilla/src/style.css
@@ -466,6 +466,39 @@ select:focus {
   --link-color: #5ac8fa;
   --border-color: #333333;
   --accent-color: #2188ff;
+  --sidebar-text-color: rgba(0, 0, 0, 0.87);
+}
+
+/* Dark mode: sidebar uses grey background with dark text */
+.theme-dark .sidebar {
+  background: rgba(180, 180, 180, 0.85);
+  border-right-color: rgba(0, 0, 0, 0.15);
+}
+
+.theme-dark .sidebar-section li a,
+.theme-dark .sidebar-section h3,
+.theme-dark .sidebar-footer a {
+  color: rgba(0, 0, 0, 0.87);
+}
+
+.theme-dark .sidebar-section li.active a {
+  background: rgba(0, 0, 0, 0.15);
+}
+
+.theme-dark .sidebar-section li a:hover {
+  background: rgba(0, 0, 0, 0.08);
+}
+
+/* Dark mode: sidebar-toggle button should have no background */
+.theme-dark .sidebar-toggle {
+  background: none;
+}
+
+/* Dark mode: sidebar search input should use light background */
+.theme-dark .sidebar-search input {
+  background: rgba(255, 255, 255, 0.7);
+  color: rgba(0, 0, 0, 0.87);
+  border-color: rgba(0, 0, 0, 0.2);
 }
 
 .font-serif {