fix: reduce app header height for compact layout (#141)

Reduces header from h-24/sm:h-28 (96/112px) to h-20/sm:h-24 (80/96px),
and BrandLogo from size="lg" to size="md" so the logo scales with the
smaller header. Layout (sticky, backdrop blur, max-width container,
right-side gap-4 stack) is preserved; items-center keeps everything
vertically centered.

Fixes #138

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

Author: mvanhorn

components/app-header.tsx

@@ -5,7 +5,7 @@ import { ThemeToggle } from "@/components/theme-toggle";
 export function AppHeader() {
   return (
     <header className="sticky top-0 z-50 w-full border-b border-border bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/60">
-      <div className="container m-auto flex h-24 max-w-7xl items-center justify-between px-4 sm:h-28">
+      <div className="container m-auto flex h-20 max-w-7xl items-center justify-between px-4 sm:h-24">
         <BrandLogo priority size="md" className="shrink-0" />
 
         <div className="flex gap-4">
@@ -15,4 +15,4 @@ export function AppHeader() {
       </div>
     </header>
   );
-}
+}