feat: scaffold Astro project with layout, nav, hero and concept sections

- Add global ocean-themed styles (Inter + Sora, glassmorphism utilities).
- Wire up base layout, sticky nav and footer respecting base path.
- Build hero with stylised rock SVG + sonar ambient rings and concept pipeline schematic.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tailwind.config.mjs

@@ -0,0 +1,72 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+  content: ['./src/**/*.{astro,html,js,jsx,md,mdx,svelte,ts,tsx,vue}'],
+  darkMode: 'class',
+  theme: {
+    extend: {
+      colors: {
+        abyss: {
+          950: '#050d1a',
+          900: '#0a1a2f',
+          800: '#0f2742',
+          700: '#143558',
+          600: '#1a4570',
+          500: '#215889',
+        },
+        tide: {
+          400: '#38bdf8',
+          500: '#0ea5e9',
+          600: '#0284c7',
+        },
+        foam: {
+          50: '#f0f9ff',
+          100: '#e0f2fe',
+          200: '#bae6fd',
+        },
+        lagoon: {
+          400: '#22d3ee',
+          500: '#06b6d4',
+          600: '#0891b2',
+        },
+        galet: {
+          300: '#94a3b8',
+          400: '#64748b',
+          500: '#475569',
+        },
+      },
+      fontFamily: {
+        sans: ['Inter', 'ui-sans-serif', 'system-ui', 'sans-serif'],
+        display: ['Sora', 'Inter', 'ui-sans-serif', 'system-ui', 'sans-serif'],
+      },
+      boxShadow: {
+        glow: '0 0 40px -10px rgba(14, 165, 233, 0.35)',
+        'glow-lg': '0 0 80px -10px rgba(6, 182, 212, 0.45)',
+        card: '0 8px 30px rgba(5, 13, 26, 0.45)',
+      },
+      backgroundImage: {
+        'abyss-grad': 'linear-gradient(180deg, #050d1a 0%, #0a1a2f 40%, #0f2742 100%)',
+        'caustic': 'radial-gradient(circle at 20% 10%, rgba(6,182,212,0.15), transparent 50%), radial-gradient(circle at 80% 80%, rgba(14,165,233,0.12), transparent 50%)',
+      },
+      keyframes: {
+        'float-slow': {
+          '0%, 100%': { transform: 'translateY(0px)' },
+          '50%': { transform: 'translateY(-12px)' },
+        },
+        'shimmer': {
+          '0%': { backgroundPosition: '-200% 0' },
+          '100%': { backgroundPosition: '200% 0' },
+        },
+        'sonar': {
+          '0%': { transform: 'scale(1)', opacity: '0.6' },
+          '100%': { transform: 'scale(3)', opacity: '0' },
+        },
+      },
+      animation: {
+        'float-slow': 'float-slow 8s ease-in-out infinite',
+        'shimmer': 'shimmer 6s linear infinite',
+        'sonar': 'sonar 3s ease-out infinite',
+      },
+    },
+  },
+  plugins: [],
+};