fix(theme): correct topbar brand link and enforce no underline

- Updated the topbar brand anchor to use a static relative path (`../../index.html`) to ensure the link works correctly in the generated documentation.
- Modified CSS for `.topbar-brand` to force `text-decoration: none!important` and added explicit rules for all link states, preventing underlines and ensuring consistent styling.

Author: MohammadRaziei

docs/python/source/_themes/ctoon/layout.html

@@ -25,7 +25,7 @@
 {# ── Topbar ───────────────────────────────────────────────────────────────── #}
 {%- block header %}
 <header class="topbar">
-    <a class="topbar-brand" href="{{ pathto(master_doc|default('index')) }}">
+    <a class="topbar-brand" href="../../index.html">
         {%- if logo_url %}
         <div class="topbar-logo"><img src="{{ logo_url|e }}" alt="CToon" width="36" height="36"></div>
         {%- endif %}

docs/python/source/_themes/ctoon/static/ctoon-sphinx.css

@@ -71,7 +71,8 @@ body {
     backdrop-filter: blur(12px);
     -webkit-backdrop-filter: blur(12px);
 }
-.topbar-brand { display: flex; align-items: center; gap: 0.75rem; text-decoration: none; color: var(--fg); }
+.topbar-brand { display: flex; align-items: center; gap: 0.75rem; text-decoration: none!important; color: var(--fg); }
+.topbar-brand a:link, .topbar-brand a:visited, .topbar-brand a:hover, .topbar-brand a:active { text-decoration: none!important; text-decoration-line: none!important; -moz-text-decoration-line: none!important;}
 .topbar-logo { width: 36px; height: 36px; display: flex; align-items: center; justify-content: center; }
 .topbar-logo svg { width: 100%; height: 100%; }
 .topbar-name { font-weight: 700; font-size: 1rem; letter-spacing: -0.02em; }