fix: Rename focusAreas → focusPreferences (duplicate state variable)

- Line 60: focusPreferences (user's legacy preferences)
- Line 74: focusAreas (focus area definitions)
- Updated all references to avoid name collision
- Fixes build error in vite

frontend/src/pages/GoalsPage.jsx

@@ -57,7 +57,7 @@ const getCategoryForGoalType = (goalType) => {
 
 export default function GoalsPage() {
   const [goalMode, setGoalMode] = useState(null)
-  const [focusAreas, setFocusAreas] = useState(null)
+  const [focusPreferences, setFocusPreferences] = useState(null) // User's legacy focus preferences
   const [focusEditing, setFocusEditing] = useState(false)
   const [focusTemp, setFocusTemp] = useState({
     weight_loss_pct: 0,
@@ -133,7 +133,7 @@ export default function GoalsPage() {
         updated_at: focusData?.updated_at
       }
 
-      setFocusAreas(sanitizedFocus)
+      setFocusPreferences(sanitizedFocus)
       setFocusTemp(sanitizedFocus)
 
       // Convert types array to map for quick lookup
@@ -422,7 +422,7 @@ export default function GoalsPage() {
         </div>
         <p style={{ color: 'var(--text2)', fontSize: 14, marginBottom: 16 }}>
           Setze relative Gewichte für deine Trainingsziele. Das System berechnet automatisch die Prozentanteile.
-          {focusAreas && !focusAreas.custom && (
+          {focusPreferences && !focusPreferences.custom && (
             <span style={{ display: 'block', marginTop: 4, fontStyle: 'italic' }}>
               ℹ️ Aktuell abgeleitet aus Trainingsmodus "{goalMode}" - klicke "Anpassen" für individuelle Gewichtung
             </span>