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/routes/+page.svelte

@@ -1,32 +1,33 @@
 <script lang="ts">
+	import { t } from 'svelte-i18n';
 	import type { PageData } from './$types.js';
 
 	let { data }: { data: PageData } = $props();
 </script>
 
 <svelte:head>
-	<title>Web App Launcher</title>
+	<title>{$t('app_title')}</title>
 </svelte:head>
 
 <div class="flex min-h-[60vh] items-center justify-center p-6">
 	<div class="text-center">
-		<h1 class="text-4xl font-bold text-foreground">Web App Launcher</h1>
+		<h1 class="text-4xl font-bold text-foreground">{$t('app_title')}</h1>
 		{#if data.user}
 			<p class="mt-4 text-muted-foreground">
-				Welcome, {data.user.displayName}. No default board is configured yet.
+				{$t('home.welcome', { values: { name: data.user.displayName } })}
 			</p>
 			<div class="mt-6 flex items-center justify-center gap-3">
 				<a
 					href="/boards"
 					class="rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground hover:bg-primary/90"
 				>
-					View Boards
+					{$t('home.view_boards')}
 				</a>
 				<a
 					href="/apps"
 					class="rounded-md border border-border px-4 py-2 text-sm font-medium text-foreground hover:bg-accent"
 				>
-					Browse Apps
+					{$t('home.browse_apps')}
 				</a>
 			</div>
 		{/if}