feat(landing): Astro-Landingpage für Cardecky

Neue statische Astro 5-App in apps/landing/ (Port 4380).
Sektionen: Nav, Hero, Kartentypen-Grid (6 Typen), How-it-works,
Features, mana-e.V.-Pitch, CTA, Footer.

Stack: Astro 5 + Tailwind 3, kein MDX (overkill für MVP), keine
externen Abhängigkeiten. Forest-grüne Farbpalette passend zum App-
Theme, Serif-Headings im mana-e.V.-Stil.

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

apps/landing/tailwind.config.cjs

@@ -0,0 +1,31 @@
+/** @type {import('tailwindcss').Config} */
+module.exports = {
+	content: ['./src/**/*.{astro,html,js,jsx,ts,tsx}'],
+	theme: {
+		extend: {
+			colors: {
+				ink:    '#111812',
+				paper:  '#f9faf7',
+				muted:  '#6b7a6e',
+				rule:   '#e2e8e0',
+				leaf:   '#16a34a',
+				'leaf-hover': '#15803d',
+				'leaf-light': '#f0fdf4',
+				'leaf-border': '#bbf7d0',
+			},
+			fontFamily: {
+				serif: ['Georgia', 'Cambria', '"Times New Roman"', 'serif'],
+				sans:  ['system-ui', '-apple-system', 'sans-serif'],
+			},
+			fontSize: {
+				hero:    ['clamp(2.25rem,5vw,3.5rem)', { lineHeight: '1.1', letterSpacing: '-0.02em' }],
+				display: ['clamp(1.75rem,3vw,2.5rem)',  { lineHeight: '1.2', letterSpacing: '-0.015em' }],
+			},
+			maxWidth: {
+				content: '68rem',
+				prose:   '44rem',
+			},
+		},
+	},
+	plugins: [],
+};