feat(HAI-089): add logo SVG to header component with tests

- Add logo.svg image element to Header component before the h1 title
- Add header-logo CSS class with sizing and flex-shrink styles
- Update header-left alignment from baseline to center
- Add Header component tests covering logo rendering and position

packages/dashboard/app/components/Header.tsx

@@ -8,6 +8,7 @@ export function Header({ onOpenSettings }: HeaderProps) {
   return (
     <header className="header">
       <div className="header-left">
+        <img src="/logo.svg" alt="hai logo" className="header-logo" width={24} height={24} />
         <h1 className="logo">hai</h1>
         <span className="logo-sub">board</span>
       </div>