fix: enable Go to Dashboard button on setup wizard final step

The "Go to Dashboard" button on Step 5 of the setup wizard was permanently
disabled because the disabled attribute checked !canGoNext, which is always
true on the last step (since canGoNext only allows advancing to the next step).

Changed the disabled attribute from:
  disabled={!canGoNext || loading}
to:
  disabled={(!canGoNext && !isLast) || loading}

This allows the button to be clickable on the final step while preserving
validation on steps 1-4. The navigate("/admin") call already handles the
last-step click correctly.

Fixes GRO-373.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/src/pages/SetupWizard.jsx

@@ -204,7 +204,7 @@ export function SetupWizard() {
           )}
           <button
             onClick={handleNext}
-            disabled={!canGoNext || loading}
+            disabled={(!canGoNext && !isLast) || loading}
             style={{
               padding: "0.55rem 1.25rem",
               borderRadius: 8,