fix(admin): say where error reports go, and stop calling a silent target configured

There is no default error-reporting DSN in this tree and there should not be:
a self-hoster's crash reports must not leave their host because nobody told
them not to. That part was already right, so nothing here adds a default.

What was wrong is what the console said about it. The GlitchTip card showed a
green "Configured" badge as soon as a DSN existed, whether or not the switch
that actually sends anything was on, and it never said where reports go. An
operator reading that badge has been told their errors are being collected
somewhere, which may be true of neither half.

The badge now tracks reports actually leaving, and one line under the switch
states the case: the host they go to, or that they stay here, or that tracking
is on with no target. The host only — the public key in the DSN answers a
different question. The deploy runbook says the same thing for a
maintainer-operated instance.

src/components/admin/glitchtip-section.tsx

@@ -34,7 +34,30 @@ export function GlitchtipSection() {
   const glitchtipEnvironmentValue =
     glitchtipEnvironmentDraft ?? settings?.glitchtipEnvironment ?? "production";
 
-  const configured = Boolean(settings?.glitchtipDsn);
+  /**
+   * The host the DSN addresses, and nothing else from it. An operator asking
+   * "where do my errors go" is asking for a hostname; the public key in the
+   * DSN answers a different question and does not belong in a status line.
+   *
+   * There is deliberately no default here and none anywhere else in the tree:
+   * a self-hoster's crash reports must not leave their host because nobody
+   * told them not to. Reporting starts when this operator types a target.
+   */
+  const targetHost = ((): string | null => {
+    const dsn = settings?.glitchtipDsn;
+    if (!dsn) return null;
+    try {
+      return new URL(dsn).host || null;
+    } catch {
+      return null;
+    }
+  })();
+
+  // "Configured" has to mean reports are actually going somewhere. A DSN with
+  // the switch off sends nothing, and a green badge over that is the kind of
+  // reassurance an operator only discovers was wrong when they go looking for
+  // a crash that was never reported.
+  const reporting = Boolean(settings?.glitchtipEnabled && targetHost);
 
   const testGlitchtip = useMutation({
     mutationFn: async () => {
@@ -76,7 +99,7 @@ export function GlitchtipSection() {
         icon={AlertTriangle}
         title={t("admin.glitchtipTitle")}
         description={t("admin.glitchtipDescription")}
-        status={configured ? <ConfiguredBadge /> : null}
+        status={reporting ? <ConfiguredBadge /> : null}
       />
 
       <div className="space-y-3">
@@ -89,6 +112,13 @@ export function GlitchtipSection() {
           }
           disabled={updateSettings.isPending}
         />
+        <p className="text-sm" data-slot="glitchtip-target">
+          {reporting && targetHost
+            ? t("admin.glitchtipTargetOn", { host: targetHost })
+            : settings?.glitchtipEnabled
+              ? t("admin.glitchtipTargetNoTarget")
+              : t("admin.glitchtipTargetOff")}
+        </p>
         <div className="grid gap-3 sm:grid-cols-2">
           <div className="space-y-1.5 sm:col-span-2">
             <Label htmlFor="admin-glitchtip-dsn" className="text-xs">