feat(FN-844): add theme-driven logo and CTA button token system

- Add CSS custom properties (--kb-logo-accent, --kb-cta-*) for logo accent color and new-task action buttons
- Update logo.svg to use currentColor for theme-aware accent stroke
- Apply tokenized styling to Header logo, QuickEntryBox, InlineCreateCard, ListView, and Column new-task buttons
- Add theme-aware test assertions for logo and CTA buttons in Header, InlineCreateCard, ListView, and QuickEntryBox tests
- Document theme token system in dashboard README

packages/dashboard/app/components/Header.tsx

@@ -242,7 +242,20 @@ export function Header({
   return (
     <header className="header">
       <div className="header-left">
-        <img src="/logo.svg" alt="Fusion logo" className="header-logo" width={24} height={24} />
+        <svg
+          className="header-logo"
+          width={24}
+          height={24}
+          viewBox="0 0 128 128"
+          fill="none"
+          aria-label="Fusion logo"
+          role="img"
+        >
+          <circle cx="44" cy="44" r="20" fill="currentColor" />
+          <circle cx="84" cy="44" r="20" fill="currentColor" />
+          <circle cx="44" cy="84" r="20" fill="currentColor" />
+          <circle cx="84" cy="84" r="20" fill="currentColor" />
+        </svg>
         <h1 className="logo">Fusion</h1>
 
         {/* Project Selector - shown when 2+ projects on desktop only */}