feat: replace brand mark with waypoint (pin-on-route) logo

Swaps the peaks-over-a-road glyph for a location pin on a route line
in both the favicon and the BrandMark component, so the mark stays
legible at 16px favicon size and reads more literally as fleet/route
tracking. Palette unchanged (navy #0f172a, teal #2dd4bf).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/Icons.tsx

@@ -64,8 +64,9 @@ export function Icon({ name, ...props }: { name: IconName } & SVGProps<SVGSVGEle
 export function BrandMark({ className = "" }: { className?: string }) {
   return (
     <svg className={className} aria-hidden="true" viewBox="0 0 32 32" fill="none">
-      <path d="M5 23V8l7.1 8L19 8h8v15h-5V14l-9.9 11L10 22.6V23H5Z" fill="currentColor" />
-      <path d="M3 15.5h26" stroke="#2dd4bf" strokeWidth="2.5" />
+      <path d="M16 25.5c-4.4-5.1-6-8.2-6-11a6 6 0 1 1 12 0c0 2.8-1.6 5.9-6 11Z" fill="currentColor" />
+      <circle cx="16" cy="14.3" r="2.1" fill="#2dd4bf" />
+      <rect x="3" y="20.6" width="26" height="2.4" rx="1.2" fill="#2dd4bf" />
     </svg>
   );
 }