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/script-builder/ScriptBuilderChat.tsx

@@ -57,7 +57,7 @@ export function ScriptBuilderChat({
         >
           {msg.role === 'assistant' && (
             <div className="shrink-0 w-8 h-8 rounded-lg bg-[rgba(96,165,250,0.1)] flex items-center justify-center mt-0.5">
-              <Bot size={16} className="text-blue-400" />
+              <Bot size={16} className="text-accent" />
             </div>
           )}
 
@@ -99,10 +99,10 @@ export function ScriptBuilderChat({
       {isLoading && (
         <div className="flex gap-3 justify-start">
           <div className="shrink-0 w-8 h-8 rounded-lg bg-[rgba(96,165,250,0.1)] flex items-center justify-center">
-            <Bot size={16} className="text-blue-400" />
+            <Bot size={16} className="text-accent" />
           </div>
           <div className="card-flat rounded-xl px-4 py-3 text-sm flex items-center gap-2">
-            <Loader2 size={14} className="animate-spin text-blue-400" />
+            <Loader2 size={14} className="animate-spin text-accent" />
             <span className="text-muted-foreground">Generating script...</span>
           </div>
         </div>