fix(marketing): add accurate social preview metadata

apps/marketing/index.html

@@ -44,6 +44,18 @@
         } catch (e) {}
       })();
     </script>
+    <meta property="og:type" content="website" />
+    <meta property="og:url" content="https://www.partha.uk/" />
+    <meta property="og:title" content="PARTHA — Repository intelligence" />
+    <meta property="og:description" content="Evidence from sealed repository snapshots. Run PARTHA on your own installation." />
+    <meta property="og:image" content="https://www.partha.uk/social-preview.png" />
+    <meta property="og:image:width" content="1200" />
+    <meta property="og:image:height" content="630" />
+    <meta property="og:image:alt" content="PARTHA repository intelligence: source, facts and evidence." />
+    <meta name="twitter:card" content="summary_large_image" />
+    <meta name="twitter:title" content="PARTHA — Repository intelligence" />
+    <meta name="twitter:description" content="Evidence from sealed repository snapshots. Run on your own installation." />
+    <meta name="twitter:image" content="https://www.partha.uk/social-preview.png" />
   </head>
   <body>
     <div id="root"></div>