fix: remove /languparent path prefix and align auth/feed flow with API

- Remove /languparent prefix from all API calls (routes are at /auth/* now)
- Align register/login token handling (JWT returned directly, no registration token)
- Feed rewritten to use new getFeedPairs endpoint with PairSentenceCard/YesNoCard/WordCard
- App.jsx: check language_native_id / language_target_id for profile completeness
- Profil.jsx: add logout button

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

src/pages/Profil.jsx

@@ -3,6 +3,28 @@ import './Profil.css'
 import { useAuth } from '../context/AuthContext'
 import { getProfilData, getActiveLearningPair, getLanguageOptions, langById } from '../api/directus'
 
+function LogoutButton() {
+  const { logout } = useAuth()
+  return (
+    <button onClick={logout} title="Abmelden" style={{
+      position: 'absolute', top: '20px', right: '4px',
+      background: 'none', border: 'none', cursor: 'pointer',
+      padding: '6px', borderRadius: '8px', color: '#9A8878',
+      display: 'flex', alignItems: 'center', justifyContent: 'center',
+      transition: 'color 0.15s, background 0.15s',
+    }}
+      onMouseEnter={e => { e.currentTarget.style.color = '#C0544A'; e.currentTarget.style.background = '#FBF0EF' }}
+      onMouseLeave={e => { e.currentTarget.style.color = '#9A8878'; e.currentTarget.style.background = 'none' }}
+    >
+      <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+        <path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4"/>
+        <polyline points="16 17 21 12 16 7"/>
+        <line x1="21" y1="12" x2="9" y2="12"/>
+      </svg>
+    </button>
+  )
+}
+
 const SKILLS = [
   { label: 'Vokabular', value: 0.78 },
   { label: 'Grammatik', value: 0.65 },
@@ -124,7 +146,8 @@ export default function Profil() {
   const streak      = profil?.streak_days ?? 0
 
   return (
-    <div className="profil">
+    <div className="profil" style={{ position: 'relative' }}>
+      <LogoutButton />
       {/* ── Header ── */}
       <div className="profil-header">
         <div className="avatar-wrap">