Fix CSS: add postcss config, safelist stagger-N, drop dead rules

The page was loading with effectively no Tailwind utility classes
because there was no postcss.config.js — Vite didn't know to run
Tailwind's PostCSS plugin. The preflight and @apply references in
src/index.css were partially working (because some Tailwind processing
was happening implicitly), but the JIT content scanner wasn't running,
so all utility classes (flex, grid, p-*, text-fg, bg-bg, …) were
missing from the build. The page rendered as unstyled HTML.

postcss.config.js — newly added. Tells Vite to run tailwindcss +
autoprefixer. Written in plain UTF-8 (the earlier draft saved as
UTF-16 with BOM, which Node couldn't parse, hence the 'Syntax Error'
in the file viewer).

tailwind.config.js — added a safelist for the dynamic
`stagger-${index}` classes used in ResultCard.tsx. The JIT
content scanner can't resolve a template literal, so without the
safelist the four matching rules (stagger-0 … stagger-4) got purged
from the build even though they're used at runtime. Adding them to
the safelist keeps them alive.

src/index.css — dropped three dead rules (card-hover, btn-primary,
gradient-bg-soft) that the modern UI redesign made unused. They
were in the file but never referenced by any .tsx, so the
content-aware purger was stripping them anyway; explicit removal
keeps the source honest.

tailwind.config.js

@@ -1,56 +1,68 @@
 /** @type {import('tailwindcss').Config} */
 export default {
-  content: ['./index.html', './src/**/*.{ts,tsx}'],
-  darkMode: 'class',
+  content: ["./index.html", "./src/**/*.{ts,tsx}"],
+  // The result cards use a dynamic class `stagger-${index}` for the
+  // per-card animation delay. Tailwind's content scanner can't statically
+  // resolve that template literal, so without the safelist the four
+  // matching rules from src/index.css get purged from the build.
+  safelist: [{ pattern: /^stagger-[0-4]$/ }],
+  darkMode: "class",
   theme: {
     extend: {
       colors: {
         // Dark mode (default) palette
         bg: {
-          DEFAULT: '#080810',
-          card: '#111118',
-          hover: '#16161f',
+          DEFAULT: "#080810",
+          card: "#111118",
+          hover: "#16161f",
         },
         // Light mode palette (applied via :root when not .dark)
         bgLight: {
-          DEFAULT: '#f8fafc',
-          card: '#ffffff',
+          DEFAULT: "#f8fafc",
+          card: "#ffffff",
         },
         border: {
-          DEFAULT: 'rgba(255, 255, 255, 0.06)',
+          DEFAULT: "rgba(255, 255, 255, 0.06)",
         },
         borderLight: {
-          DEFAULT: 'rgba(0, 0, 0, 0.08)',
+          DEFAULT: "rgba(0, 0, 0, 0.08)",
         },
         accent: {
-          primary: '#7c3aed',
-          secondary: '#06b6d4',
-          secondaryLight: '#0891b2',
+          primary: "#7c3aed",
+          secondary: "#06b6d4",
+          secondaryLight: "#0891b2",
         },
         fg: {
-          DEFAULT: '#e2e8f0',
-          muted: '#64748b',
-          dark: '#0f172a',
+          DEFAULT: "#e2e8f0",
+          muted: "#64748b",
+          dark: "#0f172a",
         },
-        tag: '#a78bfa',
+        tag: "#a78bfa",
       },
       animation: {
-        'gradient-shift': 'gradient-shift 8s ease infinite',
-        'fade-up': 'fade-up 300ms ease-out forwards',
-        'pulse-slow': 'pulse 2.5s cubic-bezier(0.4, 0, 0.6, 1) infinite',
+        "gradient-shift": "gradient-shift 8s ease infinite",
+        "fade-up": "fade-up 300ms ease-out forwards",
+        "pulse-slow": "pulse 2.5s cubic-bezier(0.4, 0, 0.6, 1) infinite",
       },
       keyframes: {
-        'gradient-shift': {
-          '0%, 100%': { backgroundPosition: '0% 50%' },
-          '50%': { backgroundPosition: '100% 50%' },
+        "gradient-shift": {
+          "0%, 100%": { backgroundPosition: "0% 50%" },
+          "50%": { backgroundPosition: "100% 50%" },
         },
-        'fade-up': {
-          '0%': { opacity: '0', transform: 'translateY(20px)' },
-          '100%': { opacity: '1', transform: 'translateY(0)' },
+        "fade-up": {
+          "0%": { opacity: "0", transform: "translateY(20px)" },
+          "100%": { opacity: "1", transform: "translateY(0)" },
         },
       },
       fontFamily: {
-        mono: ['ui-monospace', 'SFMono-Regular', 'Menlo', 'Monaco', 'Consolas', 'monospace'],
+        mono: [
+          "ui-monospace",
+          "SFMono-Regular",
+          "Menlo",
+          "Monaco",
+          "Consolas",
+          "monospace",
+        ],
       },
     },
   },