fix: admin header uses logo-mark + wordmark to match public site

The brand-contrast polish that renamed logo.* to logo-mark.* (and paired
it with a styled wordmark span) only touched the public layout. Admin
still pointed at the old asset paths, which broke visually after Phase 3
and then carried forward into Phase 4. Mirror the public header exactly
so Head Hen sees the same brand chrome inside the CMS.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/templates/admin/base.html

@@ -37,13 +37,17 @@
   <header class="site-header">
     <div class="wrap site-header__wrap">
       <a class="site-header__brand" href="/" aria-label="Chicken Babies R Us home">
+        {# Match the public header: chick-only mark + styled wordmark so
+           the admin chrome reads as the same brand. Asset paths track
+           the brand-contrast rename (logo -> logo-mark). #}
         <picture>
-          <source srcset="{{ url_for('static', path='img/logo.webp') }}" type="image/webp">
-          <img src="{{ url_for('static', path='img/logo.png') }}"
-               alt="Chicken Babies R Us"
-               height="48"
-               class="site-header__logo">
+          <source srcset="{{ url_for('static', path='img/logo-mark.webp') }}" type="image/webp">
+          <img src="{{ url_for('static', path='img/logo-mark.png') }}"
+               alt=""
+               height="56"
+               class="site-header__mark">
         </picture>
+        <span class="site-header__title">Chicken Babies R Us</span>
       </a>
 
       <nav class="site-nav" aria-label="Admin">