feat(ui): establish theme tokens and global base styles

frontend/src/App.tsx

@@ -8,7 +8,6 @@ import { ErrorBoundary } from './components/ErrorBoundary';
 import { ToastContainer } from './components/Toast';
 import { useToast } from './hooks/useToast';
 import { createContext, useContext } from 'react';
-import { colors, radius } from './theme';
 
 // Create toast context to share toast functionality across the app
 interface ToastContextType {
@@ -48,10 +47,10 @@ function App() {
   return (
     <ErrorBoundary>
       <ToastContext.Provider value={toast}>
-        <div className="min-h-screen bg-gray-50">
+        <div className="min-h-screen">
           <ToastContainer messages={toast.messages} onClose={toast.removeToast} />
 
-          <header className="bg-white shadow-sm border-b border-gray-100 ">
+          <header className="sticky top-0 z-20 border-b border-slate-200/70 bg-white/85 shadow-sm backdrop-blur-md dark:border-slate-700/60 dark:bg-slate-900/70">
             <div className="max-w-7xl mx-auto px-4">
               <div className="flex items-center justify-between h-16">
                 <div className="flex items-center">
@@ -85,7 +84,7 @@ function App() {
             </Routes>
           </main>
 
-          <footer className="bg-white border-t border-gray-100 mt-12">
+          <footer className="mt-12 border-t border-slate-200/70 bg-white/70 backdrop-blur-sm dark:border-slate-700/60 dark:bg-slate-900/45">
             <div className="max-w-7xl mx-auto py-6 px-4">
               <p className="text-center text-sm text-gray-500">
                 Recipe Manager MVP - Built with React + Vite + TypeScript

frontend/src/index.css

@@ -3,20 +3,39 @@
 @tailwind utilities;
 
 :root {
-  --text: #374151;
+  --color-primary: #2563eb;
-  --text-h: #1e293b;
+  --color-primary-dark: #1d4ed8;
-  --bg: #fff;
+  --color-primary-light: #dbeafe;
-  --bg-alt: #f9fafb;
+  --color-accent: #9333ea;
-  --border: #e5e7eb;
-  --code-bg: #f4f3ec;
-  --accent: #aa3bff;
-  --accent-bg: rgba(170, 59, 255, 0.08);
-  --accent-border: rgba(170, 59, 255, 0.35);
-  --card-shadow: 0 2px 8px 0 rgba(28,30,34,0.08);
 
-  --sans: system-ui, 'Segoe UI', Roboto, sans-serif;
+  --text: #1f2937;
-  --heading: system-ui, 'Segoe UI', Roboto, sans-serif;
+  --text-h: #0f172a;
-  --mono: ui-monospace, Consolas, monospace;
+  --text-dim: #64748b;
+
+  --bg: #f4f7fb;
+  --bg-alt: #edf2f7;
+  --surface: #ffffff;
+  --surface-muted: #f8fafc;
+  --border: #dbe3ef;
+  --code-bg: #eef2f7;
+
+  --radius-sm: 0.5rem;
+  --radius-md: 0.75rem;
+  --radius-lg: 1rem;
+
+  --shadow-subtle: 0 1px 2px rgba(15, 23, 42, 0.06);
+  --card-shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
+  --shadow-hover: 0 14px 34px rgba(15, 23, 42, 0.12);
+  --focus-ring: 0 0 0 3px rgba(37, 99, 235, 0.25);
+
+  --surface-gradient:
+    radial-gradient(1200px 500px at -10% -10%, rgba(147, 51, 234, 0.1), transparent 60%),
+    radial-gradient(900px 420px at 115% -5%, rgba(37, 99, 235, 0.08), transparent 52%),
+    linear-gradient(180deg, #f8fbff 0%, #edf2f7 100%);
+
+  --sans: Inter, system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  --heading: Inter, system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
 
   font-synthesis: none;
   text-rendering: optimizeLegibility;
@@ -26,16 +45,25 @@
 
 @media (prefers-color-scheme: dark) {
   :root {
-    --text: #d1d5db;
+    --text: #e2e8f0;
-    --text-h: #f3f4f6;
+    --text-h: #f8fafc;
-    --bg: #16171d;
+    --text-dim: #94a3b8;
-    --bg-alt: #1a1b20;
+
-    --border: #2e303a;
+    --bg: #0f172a;
-    --code-bg: #1f2028;
+    --bg-alt: #111b2e;
-    --accent: #c084fc;
+    --surface: #132136;
-    --accent-bg: rgba(192, 132, 252, 0.11);
+    --surface-muted: #172842;
-    --accent-border: rgba(192, 132, 252, 0.33);
+    --border: #22334d;
-    --card-shadow: 0 3px 14px 0 rgba(32,34,40,0.21);
+    --code-bg: #1a2942;
+
+    --shadow-subtle: 0 1px 2px rgba(2, 6, 23, 0.35);
+    --card-shadow: 0 10px 30px rgba(2, 6, 23, 0.45);
+    --shadow-hover: 0 14px 34px rgba(2, 6, 23, 0.55);
+
+    --surface-gradient:
+      radial-gradient(900px 400px at 0% -5%, rgba(147, 51, 234, 0.2), transparent 60%),
+      radial-gradient(800px 420px at 105% -10%, rgba(37, 99, 235, 0.18), transparent 55%),
+      linear-gradient(180deg, #0f172a 0%, #111b2e 100%);
   }
 }
 
@@ -43,56 +71,125 @@ body {
   margin: 0;
   font-family: var(--sans);
   color: var(--text);
-  background: var(--bg-alt);
+  background: var(--surface-gradient);
+  background-attachment: fixed;
 }
 
 #root {
   min-height: 100vh;
-  background: var(--bg-alt);
+  background: transparent;
 }
 
-input, button, textarea, select {
+input,
+button,
+textarea,
+select {
   font-family: inherit;
 }
 
+h1,
+h2,
+h3,
+h4,
+h5,
+h6 {
+  font-family: var(--heading);
+  color: var(--text-h);
+}
+
+a {
+  color: inherit;
+}
+
+button,
+.button,
+.btn {
+  border-radius: var(--radius-md);
+  border: 1px solid transparent;
+  transition: background-color 0.15s ease, color 0.15s ease, box-shadow 0.15s ease,
+    transform 0.15s ease;
+}
+
+button:hover,
+.button:hover,
+.btn:hover {
+  box-shadow: var(--shadow-subtle);
+}
+
+button:focus-visible,
+.button:focus-visible,
+.btn:focus-visible,
+input:focus-visible,
+textarea:focus-visible,
+select:focus-visible {
+  outline: none;
+  box-shadow: var(--focus-ring);
+}
+
+input,
+textarea,
+select {
+  border-radius: var(--radius-md);
+  border: 1px solid var(--border);
+  background: var(--surface);
+  color: var(--text);
+}
+
+input::placeholder,
+textarea::placeholder {
+  color: color-mix(in srgb, var(--text-dim) 70%, transparent);
+}
+
+.card,
+.shadow-card {
+  border-radius: var(--radius-lg);
+  border: 1px solid var(--border);
+  background: var(--surface);
+  box-shadow: var(--card-shadow);
+}
+
 .shadow-card {
   box-shadow: var(--card-shadow) !important;
 }
 
 /* Toast animation */
 @keyframes slide-in {
-  from { transform: translateX(100%); opacity: 0; }
+  from {
-  to { transform: translateX(0); opacity: 1; }
+    transform: translateX(100%);
+    opacity: 0;
+  }
+  to {
+    transform: translateX(0);
+    opacity: 1;
+  }
 }
 .animate-slide-in {
   animation: slide-in 0.3s ease-out;
 }
 
-/* Recipe Manager visual polish */
-
-::-webkit-input-placeholder { color: #96a3b7; }
-::-moz-placeholder { color: #96a3b7; }
-:-ms-input-placeholder { color: #96a3b7; }
-::placeholder { color: #96a3b7; }
-
-input:focus, textarea:focus, select:focus { outline: 2px solid #3b82f6; outline-offset: 2px; }
-
-button, .button, .btn {
-  transition: box-shadow 0.13s, background 0.13s, color 0.13s;
-}
-
-.card, .shadow-card { border-radius: 1rem; box-shadow: var(--card-shadow); }
-
 ::-webkit-scrollbar {
   width: 8px;
-  background: #f3f4f6;
+  background: var(--surface-muted);
 }
 ::-webkit-scrollbar-thumb {
-  background: #e5e7eb;
+  background: var(--border);
   border-radius: 7px;
 }
 
 @media (max-width: 480px) {
-  .max-w-7xl, .max-w-6xl, .max-w-4xl, .max-w-3xl, .max-w-2xl, .max-w-xl, .max-w-md, .max-w-sm { max-width: 100vw !important; }
+  .max-w-7xl,
-  .p-8, .p-7, .p-6 { padding: 1rem !important; }
+  .max-w-6xl,
+  .max-w-4xl,
+  .max-w-3xl,
+  .max-w-2xl,
+  .max-w-xl,
+  .max-w-md,
+  .max-w-sm {
+    max-width: 100vw !important;
+  }
+  .p-8,
+  .p-7,
+  .p-6 {
+    padding: 1rem !important;
+  }
 }

frontend/src/theme.ts

@@ -1,54 +1,80 @@
-/** theme.ts - Defines visual theme tokens and utility styles across the Recipe Manager frontend */
+/**
+ * Centralized design tokens for the Recipe Manager frontend.
+ * Keep values semantic so UI primitives can evolve without broad refactors.
+ */
 
 export const colors = {
-  primary: '#2563eb', // Tailwind blue-600
+  primary: '#2563eb',
   primaryDark: '#1d4ed8',
-  primaryLight: '#eff6ff',
+  primaryLight: '#dbeafe',
-  accent: '#aa3bff',
+  accent: '#9333ea',
-  success: '#16a34a',
+  success: '#15803d',
-  warning: '#eab308',
+  warning: '#ca8a04',
   error: '#dc2626',
 
-  bg: '#fff',
+  bg: '#f4f7fb',
-  bgAlt: '#f9fafb', // Tailwind gray-50
+  bgAlt: '#edf2f7',
-  surface: '#fcfcff',
+  surface: '#ffffff',
-  border: '#e5e7eb', // Tailwind gray-200
+  surfaceMuted: '#f8fafc',
-  text: '#374151', // Tailwind gray-700
+  border: '#dbe3ef',
-  textDim: '#6b7280',
-  textHeading: '#1e293b',
-  cardShadow: '0 2px 8px 0 rgba(28,30,34,0.08)',
-};
 
-export const radius = {
+  text: '#1f2937',
-  xs: '4px',
+  textDim: '#64748b',
-  sm: '6px',
+  textHeading: '#0f172a',
-  md: '10px',
-  lg: '16px',
-  full: '999px',
-};
 
-export const spacing = {
+  focusRing: '#2563eb',
-  xs: '4px',
-  sm: '8px',
-  md: '16px',
-  lg: '24px',
-  xl: '40px',
-};
-
-export const shadows = {
-  card: '0 2px 8px 0 rgba(28,30,34,0.08)',
-  hover: '0 4px 20px 0 rgba(28,30,34,0.16)',
 };
 
 export const typography = {
   fontFamily: {
-    sans: 'system-ui, Segoe UI, Roboto, sans-serif',
+    sans: "Inter, system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif",
-    heading: 'system-ui, Segoe UI, Roboto, sans-serif',
+    heading: "Inter, system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif",
-    mono: 'ui-monospace, Consolas, monospace',
+    mono: "ui-monospace, SFMono-Regular, Menlo, Consolas, monospace",
+  },
+  fontSize: {
+    xs: '0.75rem',
+    sm: '0.875rem',
+    base: '1rem',
+    lg: '1.125rem',
+    xl: '1.25rem',
+    '2xl': '1.5rem',
+    '3xl': '1.875rem',
+  },
+  lineHeight: {
+    tight: '1.2',
+    normal: '1.5',
+    relaxed: '1.65',
   },
   fontWeight: {
     regular: 400,
     medium: 500,
+    semibold: 600,
     bold: 700,
   },
 };
+
+export const spacing = {
+  xxs: '0.25rem',
+  xs: '0.5rem',
+  sm: '0.75rem',
+  md: '1rem',
+  lg: '1.5rem',
+  xl: '2rem',
+  '2xl': '2.5rem',
+};
+
+export const radius = {
+  xs: '0.375rem',
+  sm: '0.5rem',
+  md: '0.75rem',
+  lg: '1rem',
+  xl: '1.25rem',
+  full: '9999px',
+};
+
+export const shadows = {
+  subtle: '0 1px 2px rgba(15, 23, 42, 0.06)',
+  card: '0 10px 30px rgba(15, 23, 42, 0.08)',
+  hover: '0 14px 34px rgba(15, 23, 42, 0.12)',
+  focus: '0 0 0 3px rgba(37, 99, 235, 0.25)',
+};