feat(stats): resource metrics dashboard + sites logs/stats

Background collector samples CPU/memory/network/block I/O for every
instance and site on a configurable interval (default 15s, range
5-300s), persists samples to SQLite with a configurable retention
window (default 2h, range 0-24h), and skips ticks gracefully when
the Docker daemon is unreachable. Settings are reloadable without
a restart — each tick re-reads them.

New API endpoints:
- GET /api/system/stats (host snapshot: info + df)
- GET /api/system/stats/history
- GET /api/system/stats/top?by=cpu|memory
- GET /api/projects/{id}/stages/{s}/instances/{iid}/stats/history
- GET /api/sites/{id}/stats[/history]
- GET /api/sites/{id}/logs (SSE + JSON, reuses instance log streamer)

Frontend:
- ECharts added with tree-shaken imports (~180KB gzip) for
  future-proof time-series/gantt/graph visualizations
- CollapsibleSection wraps all dashboard sections (system health,
  daemons, system resources, static sites, projects) with
  localStorage-persisted open state
- SystemResourcesCard shows capacity tiles, workload utilization
  chart with 30m/2h/6h/24h window picker, disk breakdown with
  reclaimable callouts, and top 5 consumers
- ContainerStats and ContainerLogs take a source discriminated union
  so sites reuse the same components as instances; sites detail page
  embeds both for Deno backend debugging
- Settings › Maintenance exposes collection interval + retention
- Docker-unavailable state returns 503 and renders an amber banner
  instead of a generic 500

Full i18n coverage (en + ru) for all new strings.

web/src/lib/components/ContainerLogs.svelte

@@ -1,21 +1,26 @@
 <!--
   Container log viewer with tail line limit and auto-scroll.
+
+  Works for both project instances and static sites — pass a `source`
+  discriminated union to point at the right endpoint.
 -->
 <script lang="ts">
 	import { onDestroy } from 'svelte';
-	import { fetchContainerLogs } from '$lib/api';
+	import { fetchContainerLogs, fetchStaticSiteLogs } from '$lib/api';
 	import { getAuthToken } from '$lib/auth';
 	import { t } from '$lib/i18n';
 	import { IconLoader, IconX } from '$lib/components/icons';
 
+	export type LogSource =
+		| { kind: 'instance'; projectId: string; stageId: string; instanceId: string }
+		| { kind: 'site'; siteId: string };
+
 	interface Props {
-		projectId: string;
-		stageId: string;
-		instanceId: string;
+		source: LogSource;
 		onclose: () => void;
 	}
 
-	const { projectId, stageId, instanceId, onclose }: Props = $props();
+	const { source, onclose }: Props = $props();
 
 	let lines = $state<string[]>([]);
 	let loading = $state(true);
@@ -48,11 +53,26 @@
 		}
 	}
 
+	function buildFollowUrl(token: string | null): string {
+		const tokenParam = token ? `&token=${token}` : '';
+		if (source.kind === 'instance') {
+			return `/api/projects/${source.projectId}/stages/${source.stageId}/instances/${source.instanceId}/logs?follow=true&tail=0${tokenParam}`;
+		}
+		return `/api/sites/${source.siteId}/logs?follow=true&tail=0${tokenParam}`;
+	}
+
+	async function fetchLogs(tail: number): Promise<string[]> {
+		if (source.kind === 'instance') {
+			return fetchContainerLogs(source.projectId, source.stageId, source.instanceId, tail);
+		}
+		return fetchStaticSiteLogs(source.siteId, tail);
+	}
+
 	async function loadLogs() {
 		loading = true;
 		error = '';
 		try {
-			lines = await fetchContainerLogs(projectId, stageId, instanceId, tailCount);
+			lines = await fetchLogs(tailCount);
 		} catch (err) {
 			error = err instanceof Error ? err.message : 'Failed to load logs';
 		} finally {
@@ -65,8 +85,7 @@
 		if (eventSource) return;
 		following = true;
 		const token = getAuthToken();
-		const url = `/api/projects/${projectId}/stages/${stageId}/instances/${instanceId}/logs?follow=true&tail=0&token=${token}`;
-		eventSource = new EventSource(url);
+		eventSource = new EventSource(buildFollowUrl(token));
 
 		eventSource.onmessage = (e) => {
 			try {
@@ -87,7 +106,6 @@
 			eventSource.close();
 			eventSource = null;
 		}
-		// Flush any buffered lines before stopping.
 		if (flushTimer) { clearTimeout(flushTimer); flushTimer = null; }
 		flushPendingLines();
 		following = false;
@@ -108,7 +126,6 @@
 		loadLogs();
 	}
 
-	// Load on mount.
 	$effect(() => { loadLogs(); });
 
 	onDestroy(() => {
@@ -166,7 +183,7 @@
 		{:else if lines.length === 0}
 			<p class="text-gray-500">{$t('logs.noLogs')}</p>
 		{:else}
-			{#each lines as line, i}
+			{#each lines as line}
 				<div class="hover:bg-gray-900/50 px-1 -mx-1 rounded whitespace-pre-wrap break-all">{line}</div>
 			{/each}
 		{/if}