fix(chat): Conversation auf inverted FlatList — Scroll-to-bottom bulletproof

Der setTimeout(80)+onImageLoad-Ansatz war ein Timing-Hack gegen ein
strukturelles Problem (lazy Item-Measurement unter Fabric -> scrollToEnd
landet zu kurz). Stattdessen jetzt inverted FlatList: Index 0 sitzt
permanent am Bildschirmrand, neueste Nachricht immer sichtbar.

- dm.tsx: inverted + reversedMessages, Gruppen-Logik gespiegelt,
  manuellen Auto-Scroll + keyboardHeight-State entfernt
- ChatBubble.tsx: onImageLoad-Prop entfernt (obsolet)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/rebreak-native/app/dm.tsx

@@ -1,4 +1,4 @@
-import { useState, useRef, useEffect, useCallback } from 'react';
+import { useState, useRef, useEffect, useCallback, useMemo } from 'react';
 import {
   View,
   Text,
@@ -7,7 +7,6 @@ import {
   Platform,
   ActivityIndicator,
   StyleSheet,
-  Keyboard,
   KeyboardAvoidingView,
 } from 'react-native';
 import { SafeAreaView, useSafeAreaInsets } from 'react-native-safe-area-context';
@@ -59,7 +58,6 @@ export default function DmScreen() {
   const colors = useColors();
   const styles = makeStyles(colors);
   const queryClient = useQueryClient();
-  const flatRef = useRef<FlatList>(null);
   const myUserId = useAuthStore((s) => s.user?.id);
 
   const colorScheme = useThemeStore((s) => s.colorScheme);
@@ -67,7 +65,6 @@ export default function DmScreen() {
 
   const { userId } = useLocalSearchParams<{ userId: string }>();
 
-  const [keyboardHeight, setKeyboardHeight] = useState(0);
   const [messages, setMessages] = useState<ChatMsg[]>([]);
   const [partner, setPartner] = useState<DmHistoryResponse['partner'] | null>(null);
   const partnerRef = useRef<DmHistoryResponse['partner'] | null>(null);
@@ -76,24 +73,12 @@ export default function DmScreen() {
   );
   const [sending, setSending] = useState(false);
 
-  useEffect(() => {
-    const showEvent = Platform.OS === 'ios' ? 'keyboardWillShow' : 'keyboardDidShow';
-    const hideEvent = Platform.OS === 'ios' ? 'keyboardWillHide' : 'keyboardDidHide';
-    const show = Keyboard.addListener(showEvent, (e) => setKeyboardHeight(e.endCoordinates.height));
-    const hide = Keyboard.addListener(hideEvent, () => setKeyboardHeight(0));
-    return () => {
-      show.remove();
-      hide.remove();
-    };
-  }, []);
-
   // Reset aller conversation-spezifischen States wenn userId wechselt (Stack-Reuse)
   useEffect(() => {
     setMessages([]);
     setPartner(null);
     partnerRef.current = null;
     setReplyTo(null);
-    isInitialLoad.current = true;
   }, [userId]);
 
   // Lade DM-History — staleTime:0 erzwingt immer frischen Fetch (kein Cache-Hit-Bug)
@@ -175,20 +160,7 @@ export default function DmScreen() {
   );
   useDmRealtime(userId, onDmInsert, !!myUserId);
 
-  const isInitialLoad = useRef(true);
+  const reversedMessages = useMemo(() => [...messages].reverse(), [messages]);
-
-  const scrollToBottom = useCallback((animated: boolean) => {
-    setTimeout(() => flatRef.current?.scrollToEnd({ animated }), 80);
-  }, []);
-
-  // Auto-Scroll bei neuen Messages
-  useEffect(() => {
-    if (messages.length > 0) {
-      const animated = !isInitialLoad.current;
-      isInitialLoad.current = false;
-      scrollToBottom(animated);
-    }
-  }, [messages.length, scrollToBottom]);
 
   async function handleSend(payload: SendPayload) {
     if (sending) return;
@@ -308,28 +280,27 @@ export default function DmScreen() {
             </View>
           ) : (
             <FlatList
-              ref={flatRef}
+              inverted
-              data={messages}
+              data={reversedMessages}
               style={{ flex: 1 }}
               renderItem={({ item, index }) => (
                 <ChatBubble
                   msg={item}
-                  isFirstInGroup={!sameAuthor(messages[index - 1], item)}
+                  isFirstInGroup={!sameAuthor(item, reversedMessages[index + 1])}
-                  isLastInGroup={!sameAuthor(item, messages[index + 1])}
+                  isLastInGroup={!sameAuthor(reversedMessages[index - 1], item)}
                   onReply={startReply}
                   onLike={toggleLike}
                   onOpenImage={() => {}}
-                  onImageLoad={index === messages.length - 1 ? () => scrollToBottom(false) : undefined}
                 />
               )}
               keyExtractor={(m) => m.id}
-              contentContainerStyle={{ paddingTop: 12, paddingBottom: 8 }}
+              contentContainerStyle={{ paddingBottom: 12, paddingTop: 8 }}
               showsVerticalScrollIndicator={false}
             />
           )}
         </View>
 
-        <View style={{ paddingBottom: keyboardHeight > 0 ? 8 : Math.max(12, insets.bottom), backgroundColor: colors.bg }}>
+        <View style={{ paddingBottom: Math.max(12, insets.bottom), backgroundColor: colors.bg }}>
           <ChatInput
             replyTo={replyTo}
             sending={sending}

apps/rebreak-native/components/chat/ChatBubble.tsx

@@ -47,7 +47,6 @@ type Props = {
   onReply: (msg: ChatMsg) => void;
   onLike: (msg: ChatMsg) => void;
   onOpenImage: (url: string) => void;
-  onImageLoad?: () => void;
 };
 
 function formatTime(ts: string) {
@@ -76,7 +75,6 @@ export function ChatBubble({
   onReply,
   onLike,
   onOpenImage,
-  onImageLoad,
 }: Props) {
   const { t } = useTranslation();
   const colors = useColors();
@@ -203,7 +201,6 @@ export function ChatBubble({
                   contentFit="cover"
                   cachePolicy="memory-disk"
                   transition={200}
-                  onLoad={onImageLoad ? () => onImageLoad() : undefined}
                 />
                 {isImageOnly && (
                   <View style={styles.imageTimeOverlay}>