feat(auth): polish login/register with logo, gradients and animations

frontend/src/App.css

@@ -2601,3 +2601,169 @@
 .start-btn:active {
   transform: translateY(0);
 }
+
+/* ============================================================
+   AUTH PAGES — Login / Register
+   ============================================================ */
+
+@keyframes authFadeIn {
+  from { opacity: 0; transform: translateY(16px); }
+  to   { opacity: 1; transform: translateY(0); }
+}
+
+@keyframes errorShake {
+  0%, 100% { transform: translateX(0); }
+  20%       { transform: translateX(-6px); }
+  40%       { transform: translateX(6px); }
+  60%       { transform: translateX(-4px); }
+  80%       { transform: translateX(4px); }
+}
+
+@keyframes errorFadeIn {
+  from { opacity: 0; transform: translateY(-4px); }
+  to   { opacity: 1; transform: translateY(0); }
+}
+
+.auth-page {
+  min-height: 100vh;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: var(--space-6);
+  background:
+    radial-gradient(ellipse 80% 50% at 50% -10%, rgba(255, 107, 74, 0.12) 0%, transparent 60%),
+    var(--bg-primary);
+  animation: authFadeIn var(--transition-slow) ease both;
+}
+
+.auth-card {
+  width: 100%;
+  max-width: 400px;
+  background: var(--bg-card);
+  border: 1px solid var(--border-hover);
+  border-radius: var(--radius-2xl);
+  padding: var(--space-10) var(--space-8);
+  box-shadow: var(--shadow-xl), 0 0 40px rgba(255, 107, 74, 0.06);
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: var(--space-4);
+}
+
+.logo-mark {
+  width: 56px;
+  height: 56px;
+  color: var(--accent);
+  filter: drop-shadow(0 0 10px var(--accent-glow));
+  flex-shrink: 0;
+}
+
+.auth-title {
+  font-size: var(--font-2xl);
+  font-weight: 700;
+  color: var(--text-primary);
+  text-align: center;
+  margin: 0;
+}
+
+.auth-tagline {
+  font-size: var(--font-sm);
+  color: var(--text-muted);
+  text-align: center;
+  margin: 0;
+  letter-spacing: 0.02em;
+}
+
+.auth-card form {
+  width: 100%;
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-3);
+  margin-top: var(--space-2);
+}
+
+.auth-card input[type="email"],
+.auth-card input[type="password"] {
+  width: 100%;
+  background: var(--bg-elevated);
+  border: 1.5px solid var(--border);
+  border-radius: var(--radius-lg);
+  padding: var(--space-4) var(--space-5);
+  color: var(--text-primary);
+  font-size: 16px; /* prevents iOS auto-zoom */
+  transition: border-color var(--transition-base), box-shadow var(--transition-base);
+}
+
+.auth-card input[type="email"]:focus,
+.auth-card input[type="password"]:focus {
+  border-color: var(--accent);
+  box-shadow: 0 0 0 3px var(--accent-subtle);
+  outline: none;
+}
+
+.auth-card input::placeholder {
+  color: var(--text-tertiary);
+}
+
+.auth-card button[type="submit"] {
+  width: 100%;
+  padding: var(--space-4);
+  background: var(--accent);
+  color: white;
+  border: none;
+  border-radius: var(--radius-lg);
+  font-size: var(--font-base);
+  font-weight: 600;
+  cursor: pointer;
+  min-height: 52px;
+  margin-top: var(--space-2);
+  transition: background var(--transition-base), transform var(--transition-fast), box-shadow var(--transition-base);
+  box-shadow: 0 4px 14px rgba(255, 107, 74, 0.3);
+}
+
+.auth-card button[type="submit"]:hover:not(:disabled) {
+  background: var(--accent-hover);
+  transform: translateY(-1px);
+  box-shadow: 0 6px 20px rgba(255, 107, 74, 0.45);
+}
+
+.auth-card button[type="submit"]:active:not(:disabled) {
+  transform: translateY(0);
+  box-shadow: 0 2px 8px rgba(255, 107, 74, 0.3);
+}
+
+.auth-card button[type="submit"]:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+
+.auth-error {
+  width: 100%;
+  background: var(--error-subtle);
+  border: 1px solid rgba(239, 68, 68, 0.3);
+  border-radius: var(--radius-md);
+  padding: var(--space-3) var(--space-4);
+  color: #f87171;
+  font-size: var(--font-sm);
+  text-align: center;
+  animation: errorFadeIn var(--transition-base) ease both,
+             errorShake 400ms ease 100ms both;
+}
+
+.auth-link {
+  font-size: var(--font-sm);
+  color: var(--text-muted);
+  text-align: center;
+}
+
+.auth-link a {
+  color: var(--accent);
+  text-decoration: none;
+  font-weight: 500;
+  transition: color var(--transition-fast);
+}
+
+.auth-link a:hover {
+  color: var(--accent-hover);
+  text-decoration: underline;
+}

frontend/src/components/Logo.jsx

@@ -0,0 +1,9 @@
+export default function Logo() {
+  return (
+    <svg viewBox="0 0 48 48" className="logo-mark" aria-hidden="true">
+      <path d="M12 16h4v16h-4zM20 12h8v24h-8zM32 16h4v16h-4z" fill="currentColor"/>
+      <rect x="8" y="20" width="4" height="8" fill="currentColor"/>
+      <rect x="36" y="20" width="4" height="8" fill="currentColor"/>
+    </svg>
+  );
+}

frontend/src/index.css

@@ -210,6 +210,42 @@ input {
   font-size: var(--font-lg);
 }
 
+.logo-mark {
+  width: 56px;
+  height: 56px;
+  color: var(--accent);
+  margin: 0 auto var(--space-4);
+  display: block;
+}
+
+.auth-title {
+  font-size: var(--font-2xl);
+  font-weight: 700;
+  color: var(--text-primary);
+  margin-bottom: var(--space-1);
+}
+
+.auth-tagline {
+  color: var(--text-secondary);
+  font-size: var(--font-sm);
+  margin-bottom: var(--space-6);
+}
+
+@keyframes auth-error-in {
+  from {
+    opacity: 0;
+    transform: translateY(-4px);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}
+
+.auth-error {
+  animation: auth-error-in 0.2s ease-out;
+}
+
 .auth-card form {
   display: flex;
   flex-direction: column;

frontend/src/pages/LoginPage.jsx

@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { useNavigate, Link } from 'react-router-dom';
 import { useAuth } from '../context/AuthContext';
+import Logo from '../components/Logo';
 
 export default function LoginPage() {
   const [email, setEmail] = useState('');
@@ -26,9 +27,10 @@ export default function LoginPage() {
   return (
     <div className="auth-page">
       <div className="auth-card">
-        <h1>🏋️ Gravl</h1>
+        <Logo />
-        <h2>Logga in</h2>
+        <h1 className="auth-title">Logga in</h1>
-        {error && <div className="error">{error}</div>}
+        <p className="auth-tagline">Din personliga träningspartner</p>
+        {error && <div className="error auth-error">{error}</div>}
         <form onSubmit={handleSubmit}>
           <input type="email" placeholder="E-post" value={email} onChange={e => setEmail(e.target.value)} required />
           <input type="password" placeholder="Lösenord" value={password} onChange={e => setPassword(e.target.value)} required />

frontend/src/pages/RegisterPage.jsx

@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { useNavigate, Link } from 'react-router-dom';
 import { useAuth } from '../context/AuthContext';
+import Logo from '../components/Logo';
 
 export default function RegisterPage() {
   const [email, setEmail] = useState('');
@@ -26,9 +27,10 @@ export default function RegisterPage() {
   return (
     <div className="auth-page">
       <div className="auth-card">
-        <h1>🏋️ Gravl</h1>
+        <Logo />
-        <h2>Skapa konto</h2>
+        <h1 className="auth-title">Skapa konto</h1>
-        {error && <div className="error">{error}</div>}
+        <p className="auth-tagline">Börja din träningsresa</p>
+        {error && <div className="error auth-error">{error}</div>}
         <form onSubmit={handleSubmit}>
           <input type="email" placeholder="E-post" value={email} onChange={e => setEmail(e.target.value)} required />
           <input type="password" placeholder="Lösenord" value={password} onChange={e => setPassword(e.target.value)} required minLength={6} />