feat: toon positieve comments bij gelijk/gestegen gewicht (issue #17)

- 'Vetje naar beneden' als vetmassa gedaald is
- 💪 als spiermassa gestegen is
- Combineer beide op één regel indien van toepassing
- Alleen tonen bij diff >= 0 kg

src/components/LatestMeasurementCard.tsx

@@ -32,6 +32,16 @@ export default function LatestMeasurementCard({ measurements }: Props) {
   const latest = measurements[0]
   const previous = measurements[1]
   const diff = previous ? (latest.weight - previous.weight) : null
+  const fatMassDiff = previous ? (latest.fatMass - previous.fatMass) : null
+  const muscleMassDiff = previous ? (latest.muscleMass - previous.muscleMass) : null
+
+  let positiveComment: string | null = null
+  if (previous && diff !== null && diff >= 0) {
+    const parts: string[] = []
+    if (fatMassDiff !== null && fatMassDiff < 0) parts.push('Vetje naar beneden')
+    if (muscleMassDiff !== null && muscleMassDiff > 0) parts.push('💪')
+    if (parts.length > 0) positiveComment = parts.join(' ')
+  }
 
   const handleShare = async () => {
     try {
@@ -62,6 +72,9 @@ export default function LatestMeasurementCard({ measurements }: Props) {
               <Text style={styles.diffLabel}>
                 Verschil {diff !== null && (diff > 0 ? '+' : '')}{diff?.toFixed(1)} kg
               </Text>
+              {positiveComment && (
+                <Text style={styles.positiveComment}>{positiveComment}</Text>
+              )}
               <View style={styles.divider} />
             </View>
           )}
@@ -100,4 +113,5 @@ const styles = StyleSheet.create({
   previousTitle: { fontSize: 18, fontWeight: '700', marginBottom: 4 },
   previousDate: { fontSize: 14, color: '#666', marginBottom: 4 },
   diffLabel: { fontSize: 16, fontWeight: '700', color: '#2196F3' },
+  positiveComment: { fontSize: 14, color: '#4CAF50', marginTop: 4 },
 })