feat(v3): add Dozzle/Uptime Kuma/Gotify; fix Meilisearch catalogue re-index churn

- docker-compose: add dozzle, uptime-kuma, gotify services with Caddy subdomains
  (logs/uptime/push.libnovel.cc); bind-mount dozzle/users.yml for simple auth
- Caddyfile: add site blocks for logs, uptime, push subdomains
- admin layout: add Logs, Uptime, Push tabs to external tools pill
- CatalogueEntry: add Slug field; populated by novelfire scraper
- meili.Client: add BookExists() to check if a book is already indexed
- catalogue_refresh: skip books already present in Meilisearch to prevent
  redundant re-scraping and re-indexing on every runner restart
- docker-compose runner: set RUNNER_SKIP_INITIAL_CATALOGUE_REFRESH=true

v3/ui/src/routes/admin/+layout.svelte

@@ -0,0 +1,56 @@
+<script lang="ts">
+	import { page } from '$app/state';
+
+	const adminTabs = [
+		{ href: '/admin/scrape', label: 'Scrape' },
+		{ href: '/admin/audio', label: 'Audio' }
+	];
+
+	const toolTabs = [
+		{ href: 'https://feedback.libnovel.cc', label: 'Feedback' },
+		{ href: 'https://errors.libnovel.cc', label: 'Errors' },
+		{ href: 'https://analytics.libnovel.cc', label: 'Analytics' },
+		{ href: 'https://logs.libnovel.cc', label: 'Logs' },
+		{ href: 'https://uptime.libnovel.cc', label: 'Uptime' },
+		{ href: 'https://push.libnovel.cc', label: 'Push' }
+	];
+
+	interface Props {
+		children?: import('svelte').Snippet;
+	}
+	let { children }: Props = $props();
+</script>
+
+<!-- Admin nav: internal pages + external tools -->
+<div class="mb-6 flex flex-wrap items-center gap-3">
+	<!-- Internal admin pages -->
+	<div class="flex gap-1 bg-zinc-800 rounded-lg p-1 border border-zinc-700">
+		{#each adminTabs as tab}
+			<a
+				href={tab.href}
+				class="px-4 py-1.5 rounded-md text-sm font-medium transition-colors
+					{page.url.pathname.startsWith(tab.href)
+						? 'bg-zinc-700 text-zinc-100'
+						: 'text-zinc-400 hover:text-zinc-200'}"
+			>
+				{tab.label}
+			</a>
+		{/each}
+	</div>
+
+	<!-- External tools (open in new tab) -->
+	<div class="flex gap-1 bg-zinc-800 rounded-lg p-1 border border-zinc-700">
+		{#each toolTabs as tool}
+			<a
+				href={tool.href}
+				target="_blank"
+				rel="noopener noreferrer"
+				class="px-4 py-1.5 rounded-md text-sm font-medium text-zinc-400 hover:text-zinc-200 transition-colors"
+			>
+				{tool.label} ↗
+			</a>
+		{/each}
+	</div>
+</div>
+
+{@render children?.()}