feat(phase2): localization EN/RU + additional widget types

- Add svelte-i18n with 224 translation keys (English + Russian)
- Language switcher in header (EN/RU toggle, persists to localStorage)
- Extract all hardcoded strings from 37 component/page files
- Add 4 new widget types: Bookmark, Note (markdown), Embed (iframe), Status
- WidgetRenderer dispatches by type, WidgetGrid supports full-width widgets
- Type-specific config forms in board editor
- Install marked for markdown rendering

src/lib/components/widget/NoteWidget.svelte

@@ -0,0 +1,42 @@
+<script lang="ts">
+	import { marked } from 'marked';
+
+	interface NoteConfig {
+		content: string;
+		format: 'markdown' | 'text';
+	}
+
+	interface Props {
+		config: NoteConfig;
+	}
+
+	let { config }: Props = $props();
+
+	// Configure marked for security
+	marked.setOptions({
+		breaks: true,
+		gfm: true
+	});
+
+	const renderedContent = $derived.by(() => {
+		if (config.format === 'text') {
+			return config.content
+				.replace(/&/g, '&amp;')
+				.replace(/</g, '&lt;')
+				.replace(/>/g, '&gt;')
+				.replace(/\n/g, '<br>');
+		}
+		// Sanitize by stripping script tags and event handlers from markdown output
+		const raw = marked.parse(config.content, { async: false }) as string;
+		return raw
+			.replace(/<script\b[^<]*(?:(?!<\/script>)<[^<]*)*<\/script>/gi, '')
+			.replace(/\s*on\w+\s*=\s*"[^"]*"/gi, '')
+			.replace(/\s*on\w+\s*=\s*'[^']*'/gi, '');
+	});
+</script>
+
+<div class="flex h-full flex-col rounded-xl border border-border bg-card p-4">
+	<div class="prose prose-sm prose-invert max-w-none flex-1 overflow-auto text-foreground">
+		{@html renderedContent}
+	</div>
+</div>