feat: add org admin SPA for models, roles and provider

Introduce admin-web (Skeleton/SvelteKit), Prisma models for provider connection / OrgModel / OrgRole, DB-backed runtime settings, and admin API routes so org admins can manage agent configuration end-to-end.

hub/admin-web/src/lib/toast.ts

@@ -0,0 +1,34 @@
+import { writable } from 'svelte/store';
+
+export type ToastKind = 'info' | 'success' | 'error';
+
+export interface ToastItem {
+	id: number;
+	message: string;
+	kind: ToastKind;
+}
+
+let seq = 0;
+export const toasts = writable<ToastItem[]>([]);
+
+export function pushToast(message: string, kind: ToastKind = 'info', ms = 3200): void {
+	const id = ++seq;
+	toasts.update((list) => [...list, { id, message, kind }]);
+	if (ms > 0) {
+		setTimeout(() => {
+			toasts.update((list) => list.filter((t) => t.id !== id));
+		}, ms);
+	}
+}
+
+export function dismissToast(id: number): void {
+	toasts.update((list) => list.filter((t) => t.id !== id));
+}
+
+export function toastSuccess(message: string): void {
+	pushToast(message, 'success');
+}
+
+export function toastError(message: string): void {
+	pushToast(message, 'error', 5000);
+}