Fix light-dark scroll bars

ui/src/styles.css

@@ -3,6 +3,8 @@
 /* shadcn-style theme tokens (zinc placeholder palette — tweak freely).
    The app follows the OS light/dark preference automatically. */
 :root {
+  /* Native UI (scrollbars, form controls) follows the OS unless a theme is forced. */
+  color-scheme: light dark;
   --background: oklch(1 0 0);
   --foreground: oklch(0.141 0.005 285.823);
   --card: oklch(1 0 0);
@@ -33,7 +35,12 @@
 
 /* Dark tokens apply when the user forces dark, or follows a dark system theme.
    (data-theme is set by SettingsService; absent = follow the system.) */
+:root[data-theme='light'] {
+  color-scheme: light;
+}
+
 :root[data-theme='dark'] {
+  color-scheme: dark;
   --background: oklch(0.141 0.005 285.823);
   --foreground: oklch(0.985 0 0);
   --card: oklch(0.21 0.006 285.885);
@@ -89,12 +96,6 @@
   }
 }
 
-@media (prefers-color-scheme: dark) {
-  :root[data-theme='light'] {
-    color-scheme: light;
-  }
-}
-
 @theme inline {
   --color-background: var(--background);
   --color-foreground: var(--foreground);