analytics: fix Marlin endpoint URL double-encoding in head.html

Hugo's html/template JS-escapes string values inside <script> blocks.
Calling jsonify per-field produced quoted strings like "https://..."
which were then re-escaped, embedding literal quote characters in the
endpoint value passed to the SDK.

Fix by jsonifying the whole config dict at once and marking it safeJS
so html/template does not apply a second round of escaping.

Also extract the environment ternary out of the Marlin constructor call
for readability.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/js/src/marlin.js

@@ -3,15 +3,14 @@ import { Marlin, Environment } from "@docker/marlin-sdk-web-public";
 const config = window.__marlinConfig;
 
 if (config && config.apiKey && config.endpoint) {
+  const environment =
+    config.environment === "staging" ? Environment.STAGING : Environment.PROD;
   try {
     window.marlin = new Marlin({
       endpoint: config.endpoint,
       apiKey: config.apiKey,
       site: "docs",
-      environment:
-        config.environment === "staging"
-          ? Environment.STAGING
-          : Environment.PROD,
+      environment,
     });
   } catch (err) {
     console.warn("Marlin SDK init failed:", err);

layouts/_partials/head.html

@@ -82,11 +82,7 @@
   {{- end -}}
   {{- if and $apiKey $endpoint -}}
     <script>
-      window.__marlinConfig = {
-        apiKey: {{ $apiKey | jsonify }},
-        endpoint: {{ $endpoint | jsonify }},
-        environment: {{ $env | jsonify }}
-      };
+      window.__marlinConfig = {{ dict "apiKey" $apiKey "endpoint" $endpoint "environment" $env | jsonify | safeJS }};
     </script>
   {{- end -}}
 {{- end -}}