feat: UI overhaul - component library + route layouts with instant headers

- Created 11 reusable UI components: PageHeader, SectionCard, StatCard, StatusBadge, TabBar, MemberList, ActivityFeed, EventCard, ContentSkeleton, QuickLinkGrid, ModuleCard
- Created route-specific +layout.svelte for documents, calendar, kanban, events, settings, account
- Each layout renders PageHeader instantly from parent data, shows ContentSkeleton during navigation
- Removed full-page PageSkeleton from parent layout
- Refactored all pages to use new components instead of inline markup
- Overview page: uses StatCard, SectionCard, EventCard, ActivityFeed, MemberList, QuickLinkGrid
- Events list: uses EventCard, Button components
- Event detail: uses ModuleCard, SectionCard
- Settings/Account/Calendar/Kanban: headers in layouts, toolbars in pages
- Added i18n keys for overview page (EN + ET)
- 0 errors, 112 tests pass

src/routes/[orgSlug]/calendar/+layout.svelte

@@ -0,0 +1,31 @@
+<script lang="ts">
+	import type { Snippet } from "svelte";
+	import { navigating } from "$app/stores";
+	import { PageHeader, ContentSkeleton } from "$lib/components/ui";
+	import * as m from "$lib/paraglide/messages";
+
+	interface Props {
+		data: {
+			org: { id: string; name: string; slug: string };
+		};
+		children: Snippet;
+	}
+
+	let { data, children }: Props = $props();
+
+	const isNavigatingHere = $derived(
+		$navigating?.to?.url.pathname.includes("/calendar") ?? false,
+	);
+</script>
+
+<div class="flex flex-col h-full overflow-hidden">
+	<PageHeader title={m.nav_calendar()} icon="calendar_today" iconColor="text-blue-400" />
+
+	{#if isNavigatingHere}
+		<ContentSkeleton variant="calendar" />
+	{:else}
+		<div class="flex-1 overflow-auto">
+			{@render children()}
+		</div>
+	{/if}
+</div>