refactor: normalize FlowPilot/Assistant/ScriptBuilder to design system tokens

Replace hardcoded Tailwind color utilities with semantic CSS variable tokens
across 31 files in the FlowPilot, Assistant Chat, and Script Builder feature
communities — the areas graphify identified as design-system-free.

- text-blue-400 → text-accent, bg-blue-500/10 → bg-accent-dim, border-blue-500/20 → border-accent/20
- text-amber-400 → text-warning, bg-amber-400/10 → bg-warning-dim, border-l-amber-500 → border-l-warning
- text-rose-400/500 → text-danger, bg-rose-500/10 → bg-danger-dim
- text-emerald-400 → text-success, bg-emerald-500/10 → bg-success-dim, border-l-emerald-500 → border-l-success
- bg-white/[0.08] → bg-elevated (opacity hack → semantic surface token)
- bg-gradient-to-r from-blue-500 to-blue-400 → bg-accent (no gradient surfaces)
- bg-[#60a5fa] → bg-accent (hard-coded hex removed)

Also adds graphify-out/ to .gitignore.

Theme resilience: accent color has changed twice in 5 weeks. Semantic tokens
mean the next change is a 1-line edit in index.css, not 110 grep-and-replace.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/assistant/ChatMessage.tsx

@@ -17,7 +17,7 @@ export function ChatMessage({ role, content, suggestedFlows }: ChatMessageProps)
         className={`shrink-0 w-8 h-8 rounded-full flex items-center justify-center ${
           role === 'assistant'
             ? 'bg-primary/15 text-primary'
-            : 'bg-white/[0.08] text-muted-foreground'
+            : 'bg-elevated text-muted-foreground'
         }`}
       >
         {role === 'assistant' ? <Sparkles size={14} /> : <User size={14} />}