feat: Complete light mode implementation with semantic theme system (#450)

- Add comprehensive light/dark mode CSS variables with semantic naming
- Implement theme-aware scrollbars using CSS variables
- Add light mode backgrounds: --bg-base, --bg-elevated, --bg-surface, etc.
- Add theme-aware borders: --border-base, --border-panel, --border-subtle
- Add semantic text colors: --foreground-secondary, --foreground-subtle
- Convert oklch colors to hex for better compatibility
- Add theme awareness to CodeMirror editors
- Update dark mode colors for consistency (background, sidebar, card, muted, input)
- Add Tailwind color mappings for semantic classes

Co-authored-by: Luke Gustafson <88517757+LukeGus@users.noreply.github.com>

src/ui/desktop/user/PasswordReset.tsx

@@ -67,7 +67,7 @@ export function PasswordReset({ userInfo }: PasswordResetProps) {
 
   const Spinner = (
     <svg
-      className="animate-spin mr-2 h-4 w-4 text-white inline-block"
+      className="animate-spin mr-2 h-4 w-4 text-foreground inline-block"
       viewBox="0 0 24 24"
     >
       <circle