Apply UGA brand visual identity and accessibility improvements

Restyle site to align with brand.uga.edu guidelines: Bulldog Red primary,
Olympic/Lake Herrick accents, Oswald headings, Merriweather Sans body text.
Add WCAG AA-compliant dark mode, skip-to-content link, focus indicators,
and underlined content links for Section 508 compliance.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

overrides/main.html

@@ -0,0 +1,49 @@
+{% extends "base.html" %}
+
+{# ── Accessibility: lang attribute is set by Material from mkdocs.yml
+     This override adds a skip-to-content link and improved landmarks ── #}
+
+{% block htmltitle %}
+<title>{{ config.site_name }}{% if page and page.title %} — {{ page.title }}{% endif %}</title>
+{% endblock %}
+
+{% block header %}
+{# Skip navigation link — visible on focus for keyboard users #}
+<a href="#content" class="skip-link">
+  Skip to main content
+</a>
+{{ super() }}
+{% endblock %}
+
+{% block styles %}
+{{ super() }}
+<style>
+  /* Skip-to-content link — hidden until focused */
+  .skip-link {
+    position: absolute;
+    top: -100%;
+    left: 1rem;
+    z-index: 999;
+    padding: 0.75em 1.5em;
+    background: #004E60;
+    color: #FFFFFF;
+    font-family: "Merriweather Sans", sans-serif;
+    font-weight: 700;
+    font-size: 0.9rem;
+    border-radius: 0 0 8px 8px;
+    text-decoration: none;
+    transition: top 0.2s ease;
+  }
+  .skip-link:focus {
+    top: 0;
+    outline: 3px solid #00A3AD;
+    outline-offset: 2px;
+  }
+</style>
+{% endblock %}
+
+{% block content %}
+<main id="content" role="main" tabindex="-1">
+  {{ super() }}
+</main>
+{% endblock %}