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/components/ErrorBanner.svelte

@@ -0,0 +1,26 @@
+<script lang="ts">
+	let {
+		message,
+		onretry
+	}: {
+		message: string;
+		onretry?: () => void;
+	} = $props();
+</script>
+
+<div class="saas-card flex flex-wrap items-start gap-3 border-error-200 bg-error-50 p-4 text-error-700">
+	<svg class="mt-0.5 h-5 w-5 shrink-0" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75">
+		<path
+			stroke-linecap="round"
+			stroke-linejoin="round"
+			d="M12 9v3.75m9-.75a9 9 0 11-18 0 9 9 0 0118 0zm-9 3.75h.008v.008H12v-.008z"
+		/>
+	</svg>
+	<div class="min-w-0 flex-1">
+		<p class="text-sm font-medium">请求失败</p>
+		<p class="mt-0.5 text-sm opacity-90">{message}</p>
+	</div>
+	{#if onretry}
+		<button type="button" class="saas-btn-ghost text-sm" onclick={onretry}>重试</button>
+	{/if}
+</div>