refactor: replace hardcoded hex values with Tailwind semantic tokens

3,200+ hardcoded color values replaced with CSS variable-backed
Tailwind classes (bg-card, text-foreground, border-border, etc.).
Enables light mode via CSS variable swap. Only syntax highlighting
colors and intentional one-offs remain hardcoded (~15 values).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/scripts/PowerShellHighlighter.tsx

@@ -40,7 +40,7 @@ const TOKEN_CLASSES: Record<string, string> = {
   string: 'text-[#a5d6ff]',
   placeholder: 'text-amber-400 underline decoration-dashed',
   variable: 'text-[#79c0ff]',
-  cmdlet: 'text-[#22d3ee]',
+  cmdlet: 'text-primary',
   parameter: 'text-[#d2a8ff]',
   keyword: 'text-[#ff7b72]',
 }