Add configurable service proxy (#1280)

* Add configurable service proxy

* Fix service proxy URL used when opening scripts with a public base URL

When a public proxy URL was configured, the View link was falling through
to direct connection logic and opening the wrong URL. Move the public URL
early-return before connection-type checks, and remove the now-dead
duplicate check further down.

* Add service proxy documentation

Covers config options, URL generation format, wildcard DNS setup,
and reverse proxy Host header requirements.

* Cap combined public service label and document hostname format

* Address service proxy review feedback

packages/app/src/utils/workspace-script-links.ts

@@ -14,6 +14,19 @@ function isLoopbackHost(host: string): boolean {
   );
 }
 
+function isLocalOnlyUrl(url: string | null | undefined): boolean {
+  if (!url) {
+    return true;
+  }
+  try {
+    const parsed = new URL(url);
+    const hostname = parsed.hostname.toLowerCase();
+    return isLoopbackHost(hostname) || hostname.endsWith(".localhost");
+  } catch {
+    return true;
+  }
+}
+
 function buildDirectServiceUrl(endpoint: string, port: number): string | null {
   try {
     const { host, isIpv6 } = parseHostPort(endpoint);
@@ -37,6 +50,12 @@ export function resolveWorkspaceScriptLink(input: {
     return { openUrl: null, labelUrl: script.proxyUrl };
   }
 
+  const proxyUrlIsLocalOnly = isLocalOnlyUrl(script.proxyUrl);
+
+  if (!proxyUrlIsLocalOnly) {
+    return { openUrl: script.proxyUrl, labelUrl: script.proxyUrl };
+  }
+
   if (activeConnection.type === "relay") {
     return { openUrl: null, labelUrl: script.proxyUrl };
   }