fix(admin): danger-zone result colour driven by mutation state

P18. Replace the brittle "wipeMsg.startsWith(localized prefix)" success
heuristic with React Query's `wipeAllData.isError` flag. The previous
heuristic (a) re-formatted the success copy with empty placeholders to
extract a prefix, (b) string-prefix-matched against the rendered
message, and (c) silently broke whenever the i18n copy changed colon
position or got translated. Now the colour follows the mutation state
directly: error → destructive, success → dracula-green.

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

src/components/admin/danger-zone-section.tsx

@@ -113,7 +113,9 @@ export function DangerZoneSection({ id }: { id: string }) {
         </div>
         {wipeMsg && (
           <p
-            className={`mt-2 text-sm ${wipeMsg.startsWith(t("admin.deletedResult", { measurements: "", medications: "", intakeEvents: "", apiTokens: "", withingsConnections: "", authChallenges: "" }).split(":")[0]) ? "text-dracula-green" : "text-destructive"}`}
+            className={`mt-2 text-sm ${
+              wipeAllData.isError ? "text-destructive" : "text-dracula-green"
+            }`}
           >
             {wipeMsg}
           </p>