Fix service workers

site/src/env.d.ts

@@ -4,6 +4,7 @@ interface ImportMetaEnv {
   readonly PUBLIC_SITE_URL?: string;
   readonly PUBLIC_UMAMI_SCRIPT_URL?: string;
   readonly PUBLIC_UMAMI_WEBSITE_ID?: string;
+  readonly PUBLIC_ENABLE_SW?: string;
 }
 
 interface ImportMeta {

site/src/layouts/BaseLayout.astro

@@ -57,8 +57,9 @@ const canonicalUrl = `${siteUrl}${canonicalPath.startsWith("/") ? canonicalPath
     }
 
     {
-      // Register SW only in production builds (Astro sets import.meta.env.PROD at build time).
-      import.meta.env.PROD ? (
+      // Register SW only in production builds (Astro sets import.meta.env.PROD at build time)
+      // and only when explicitly enabled by env.
+      import.meta.env.PROD && import.meta.env.PUBLIC_ENABLE_SW === "true" ? (
         <script is:inline>
           {`
           if ("serviceWorker" in navigator) {