feat: add About settings page with version and project info

Add /settings/about page showing version, project description,
Bretzel ecosystem info, open source details, and tech stack.
Move version display from sidebar to About page and align
Settings nav item styling with other sidebar items.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/components/Layout/Sidebar.svelte

@@ -6,10 +6,9 @@
 	interface Props {
 		open: boolean;
 		onClose?: () => void;
-		appVersion?: string;
 	}
 
-	let { open, onClose, appVersion }: Props = $props();
+	let { open, onClose }: Props = $props();
 
 	function closeMobile() {
 		if (window.matchMedia('(max-width: 1023px)').matches) {
@@ -75,17 +74,12 @@
 	<div class="absolute bottom-0 left-0 w-full border-t border-[var(--border-subtle)]">
 		<a
 			href="/settings"
-			class="flex w-full items-center gap-3 px-6 py-3 text-sm text-[var(--text-muted)] transition-colors hover:text-[var(--primary)]"
+			class="flex w-full items-center gap-3 rounded-sm px-6 py-3 text-left text-sm transition-colors {$page.url.pathname.startsWith('/settings') ? 'bg-[var(--primary)]/15 text-[var(--primary)]' : 'text-[var(--text)] hover:bg-[var(--bg-base)]'}"
 			onclick={closeMobile}
 			data-testid="settings-link"
 		>
-			<Settings size={16} />
+			<Settings size={20} />
 			Settings
 		</a>
-		{#if appVersion}
-			<div class="border-t border-[var(--border-subtle)] px-6 py-2 text-right text-xs text-[var(--text-muted)]">
-				v{appVersion}
-			</div>
-		{/if}
 	</div>
 </aside>