Add Plausible analytics snippet to homepage <head>

User-supplied, private self-hosted Plausible instance. Snippet inserted verbatim (unmodified,
byte-for-byte) as the last thing in <head> of index.html only, immediately before </head>.
No other page touched; no CSP exists on the site so no policy change needed.

Checks: verify-html.py PROBLEMS 0; node --check script.js OK; tracker script HTTP 200
application/javascript.

index.html

@@ -212,6 +212,12 @@
     </style>
     <link rel="stylesheet" href="style.css" media="print" onload="this.media='all'" />
     <noscript><link rel="stylesheet" href="style.css" /></noscript>
+  <!-- Privacy-friendly analytics by Plausible -->
+<script async src="https://plausible.office.odoo4projects.com/js/pa-NhA7Rf-79VopXFQXhSS4e.js"></script>
+<script>
+  window.plausible=window.plausible||function(){(plausible.q=plausible.q||[]).push(arguments)},plausible.init=plausible.init||function(i){plausible.o=i||{}};
+  plausible.init()
+</script>
 </head>
   <body>
     <!--