fix(admin-web): break /admin/login returnTo redirect loop in dev

vite dev only proxied /api and /auth, so /admin/login hit the SPA root
layout, re-ran loadSession, got 401, and redirected back to /admin/login
with an ever-nesting returnTo. Proxy /admin/login to the backend (which
owns it before the SPA fallback) and guard redirectToLogin against
re-entering /admin/login.

Replace the only emoji-as-icon (the back-arrow on project detail) with
the Icon component (new arrow-left glyph).

Add scripts/dev-bootstrap.ts for seeding a local Silo (stub probes) so
npm run dev can start on a fresh dev DB.

hub/admin-web/src/routes/admin/org/[slug]/projects/[projectId]/+page.svelte

@@ -15,6 +15,7 @@
 	import ErrorBanner from '$lib/components/ErrorBanner.svelte';
 	import EmptyState from '$lib/components/EmptyState.svelte';
 	import SelectField from '$lib/components/SelectField.svelte';
+	import Icon from '$lib/components/Icon.svelte';
 	import { toastError, toastSuccess } from '$lib/toast';
 
 	const slug = $derived(page.params.slug ?? '');
@@ -158,7 +159,8 @@
 			href={`/admin/org/${slug}/projects`}
 			class="inline-flex items-center gap-1 text-sm text-surface-700 hover:text-primary-600"
 		>
-			← 返回项目列表
+			<Icon name="arrow-left" class="h-4 w-4" />
+			返回项目列表
 		</a>
 	</div>