feat: public events/polls, friends graph, captcha, SSE hardening, and admin UX

Ship product gaps: register/vote pages, friend add/accept/decline/remove, email verify TTL, captcha on login/forgot, soft-fail user actions, SSE abort/shared client, Commando Centrum error toasts, admin delete for events/polls, and IT/NL i18n fills.

Co-authored-by: Cursor <[email protected]>

src/app/(site)/events/[slugOrId]/event-register-button.tsx

@@ -0,0 +1,42 @@
+"use client";
+
+import { useTranslations } from "next-intl";
+import { registerForEvent } from "@/actions/events";
+import { useServerAction } from "@/hooks/use-server-action";
+
+export function EventRegisterButton({
+	eventId,
+	disabled,
+	disabledReason,
+}: {
+	eventId: number;
+	disabled?: boolean;
+	disabledReason?: string;
+}) {
+	const t = useTranslations("pages.events");
+	const { run, isPending } = useServerAction();
+
+	if (disabled) {
+		return (
+			<p className="muted" style={{ margin: 0 }}>
+				{disabledReason ?? t("cannotRegister")}
+			</p>
+		);
+	}
+
+	return (
+		<button
+			type="button"
+			className="btn btn-primary"
+			disabled={isPending}
+			onClick={() =>
+				run(() => registerForEvent({ eventId }), {
+					successMessage: t("registerSuccess"),
+					errorMessage: t("registerError"),
+				})
+			}
+		>
+			{isPending ? t("registering") : t("register")}
+		</button>
+	);
+}