fix: Inverted FlatList - newest messages always visible at bottom

- No more scrollToEnd/scrollToIndex needed
- FlatList inverted=true with reversed data
- New messages appear at bottom automatically
- User scrolls up to see history (natural chat behavior)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/src/screens/ChatScreen.tsx

@@ -5,7 +5,7 @@
  * Datei- und Kamera-Upload.
  */
 
-import React, { useState, useEffect, useRef, useCallback } from 'react';
+import React, { useState, useEffect, useRef, useCallback, useMemo } from 'react';
 import {
   View,
   Text,
@@ -369,42 +369,8 @@ const ChatScreen: React.FC = () => {
     return () => { if (saveTimer.current) clearTimeout(saveTimer.current); };
   }, [messages]);
 
-  // Auto-Scroll: immer zur letzten Nachricht springen
-  const shouldAutoScroll = useRef(true);
-  const lastMessageCount = useRef(0);
-
-  // Bei neuen Nachrichten oder App-Start: nach unten springen
-  useEffect(() => {
-    if (messages.length > 0 && shouldAutoScroll.current) {
-      const isInitial = lastMessageCount.current === 0;
-      const scrollToBottom = () => {
-        try {
-          flatListRef.current?.scrollToIndex({
-            index: messages.length - 1,
-            animated: !isInitial,
-            viewPosition: 1, // 1 = Item am unteren Rand
-          });
-        } catch {
-          // Fallback wenn Index nicht berechnet werden kann
-          flatListRef.current?.scrollToEnd({ animated: !isInitial });
-        }
-      };
-      const delays = isInitial ? [200, 500, 1000] : [150];
-      for (const delay of delays) {
-        setTimeout(scrollToBottom, delay);
-      }
-    }
-    lastMessageCount.current = messages.length;
-  }, [messages]);
-
-  const handleScrollBeginDrag = useCallback(() => {
-    shouldAutoScroll.current = false;
-  }, []);
-  const handleScrollEndDrag = useCallback((e: any) => {
-    const { contentOffset, contentSize, layoutMeasurement } = e.nativeEvent;
-    const isAtBottom = contentOffset.y + layoutMeasurement.height >= contentSize.height - 50;
-    shouldAutoScroll.current = isAtBottom;
-  }, []);
+  // Inverted FlatList: neueste Nachrichten unten, kein manuelles Scrollen noetig
+  const invertedMessages = useMemo(() => [...messages].reverse(), [messages]);
 
   // GPS-Position holen (optional)
   const getCurrentLocation = useCallback((): Promise<{ lat: number; lon: number } | null> => {
@@ -693,18 +659,12 @@ const ChatScreen: React.FC = () => {
       {/* Nachrichtenliste */}
       <FlatList
         ref={flatListRef}
-        data={searchQuery ? messages.filter(m => m.text.toLowerCase().includes(searchQuery.toLowerCase())) : messages}
+        inverted
+        data={searchQuery ? messages.filter(m => m.text.toLowerCase().includes(searchQuery.toLowerCase())).reverse() : invertedMessages}
         keyExtractor={item => item.id}
         renderItem={renderMessage}
         contentContainerStyle={styles.messageList}
         showsVerticalScrollIndicator={false}
-        onScrollBeginDrag={handleScrollBeginDrag}
-        onScrollEndDrag={handleScrollEndDrag}
-        onScrollToIndexFailed={(info) => {
-          setTimeout(() => {
-            flatListRef.current?.scrollToEnd({ animated: false });
-          }, 200);
-        }}
         ListEmptyComponent={
           <View style={styles.emptyContainer}>
             <Text style={styles.emptyIcon}>{'\uD83E\uDD16'}</Text>