fix(bugreport): admin toggle now actually blocks feedback submissions

The "Bug reports" admin toggle had no effect. The form on `/bugreport`
posts to `/api/feedback`, which was the wrong endpoint for the gate —
it lived only on the legacy `/api/bugreport` route the form does not
call. Users still submitted into the local feedback inbox after the
admin disabled the feature, and the prior commit message claimed
"the report button gracefully disappears" was untrue.

- `/api/bugreport/status` now also returns `enabled` (defaults true
  when the column has never been written) so the page can decide
  whether to render the form at all.
- `/api/feedback` POST checks `bugReportEnabled` and returns 503 with
  a readable error when the admin has switched the feature off, so a
  scripted client cannot bypass the UI by hitting the endpoint directly.
- `/bugreport` page now hides the form and shows the disabled-banner
  copy when `enabled === false`.
- New i18n keys for the disabled state in DE + EN.
- Vitest covers the gate: blocked when off, allowed when on, allowed
  when row absent.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/api/bugreport/status/route.ts

@@ -29,7 +29,11 @@ export const GET = apiHandler(async () => {
 
   const appSettings = await prisma.appSettings.findUnique({
     where: { id: "singleton" },
-    select: { githubIssueTokenEncrypted: true, githubIssueRepo: true },
+    select: {
+      githubIssueTokenEncrypted: true,
+      githubIssueRepo: true,
+      bugReportEnabled: true,
+    },
   });
 
   const hasToken = Boolean(
@@ -39,11 +43,13 @@ export const GET = apiHandler(async () => {
     appSettings?.githubIssueRepo || process.env.GITHUB_ISSUE_REPO,
   );
   const configured = hasToken && hasRepo;
+  // Default ON when the column has never been written.
+  const enabled = appSettings?.bugReportEnabled !== false;
 
   annotate({
     action: { name: "bugreport.status" },
-    meta: { configured, has_token: hasToken, has_repo: hasRepo },
+    meta: { configured, enabled, has_token: hasToken, has_repo: hasRepo },
   });
 
-  return apiSuccess({ configured, isAdmin: user.role === "ADMIN" });
+  return apiSuccess({ configured, enabled, isAdmin: user.role === "ADMIN" });
 });