fix(settings): align hub page with V2 spec — padding, H1, card radius/padding/sizes

- Content area: p-[16px_20px] md:p-[40px_56px], max-w-[820px] grid
- H1: display font, 28px, weight 500, tracking -0.02em
- Cards: --radius-xl, p-[28px], shadow-card
- Card title: 16px (was 14px)
- Stat number: 28px font-light tracking-[-0.02em] (was 36px)

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

frontend/src/lib/components/SettingsCard.svelte

@@ -13,10 +13,10 @@
 <a
 	{href}
 	data-accent={accent ? 'true' : undefined}
-	class="flex flex-col gap-3 rounded-[var(--radius-md)] border border-[var(--color-border)] bg-[var(--color-surface)] p-4 no-underline text-[var(--color-text)] hover:shadow-[var(--shadow-raised)] hover:border-[#C0BFB8] transition-[box-shadow,border-color] duration-150 ease focus-visible:outline focus-visible:outline-2 focus-visible:outline-[var(--green-dark)] focus-visible:outline-offset-2"
+	class="flex flex-col gap-3 rounded-[var(--radius-xl)] border border-[var(--color-border)] bg-[var(--color-surface)] p-[28px] no-underline text-[var(--color-text)] shadow-[var(--shadow-card)] hover:shadow-[var(--shadow-raised)] hover:border-[#C0BFB8] transition-[box-shadow,border-color] duration-150 ease focus-visible:outline focus-visible:outline-2 focus-visible:outline-[var(--green-dark)] focus-visible:outline-offset-2"
 	style={accent ? 'border-left: 3px solid var(--green-dark);' : undefined}
 >
-	<span class="font-[var(--font-sans)] text-[14px] font-medium text-[var(--color-text)]">
+	<span class="font-[var(--font-sans)] text-[16px] font-medium text-[var(--color-text)]">
 		{title}
 	</span>