feat(app): Pinch-Zoom + Pan im Vollbild-Modal

Neue ZoomableImage-Komponente — reine RN-Implementation mit
PanResponder + Animated, ohne extra Dependency.

- 2-Finger-Pinch: Zoom 1x..5x, Focal-Point folgt der Geste
- 1-Finger-Pan: nur aktiv wenn gezoomt, mit Bounds-Clamping
- Doppel-Tap: Toggle 1x ↔ 2.5x

Vollbild-Modal ersetzt das simple <Image> durch ZoomableImage fuer
JPEG/PNG/etc. SVGs bleiben non-zoomable (SvgUri-Limitation), Tap
schliesst sie. Plus dedicated ✕-Close-Button oben rechts da Tap-to-
Close mit PanResponder kollidiert.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/src/screens/ChatScreen.tsx

@@ -26,6 +26,8 @@ import {
 import AsyncStorage from '@react-native-async-storage/async-storage';
 import RNFS from 'react-native-fs';
 import { SvgUri } from 'react-native-svg';
+import { Dimensions } from 'react-native';
+import ZoomableImage from '../components/ZoomableImage';
 import rvs, { RVSMessage, ConnectionState } from '../services/rvs';
 import audioService from '../services/audio';
 import wakeWordService from '../services/wakeword';
@@ -1378,25 +1380,32 @@ const ChatScreen: React.FC = () => {
 
       {/* Bild-Vollbild Modal */}
       <Modal visible={!!fullscreenImage} transparent animationType="fade" onRequestClose={() => setFullscreenImage(null)}>
-        <TouchableOpacity
-          style={styles.fullscreenOverlay}
-          activeOpacity={1}
-          onPress={() => setFullscreenImage(null)}
-        >
+        <View style={styles.fullscreenOverlay}>
           {fullscreenImage && (
             /\.svg(?:\?|$)/i.test(fullscreenImage) ? (
-              <View style={styles.fullscreenImage}>
+              // SVG: bisher keine Pinch-Zoom — Tap zum Schliessen
+              <TouchableOpacity style={styles.fullscreenImage} activeOpacity={1} onPress={() => setFullscreenImage(null)}>
                 <SvgUri uri={fullscreenImage} width="100%" height="100%" preserveAspectRatio="xMidYMid meet" />
-              </View>
+              </TouchableOpacity>
             ) : (
-              <Image
-                source={{ uri: fullscreenImage }}
+              // Pixel-Bild: Pinch-Zoom + Pan ueber ZoomableImage
+              <ZoomableImage
+                uri={fullscreenImage}
+                containerWidth={Dimensions.get('window').width}
+                containerHeight={Dimensions.get('window').height}
                 style={styles.fullscreenImage}
-                resizeMode="contain"
               />
             )
           )}
-        </TouchableOpacity>
+          {/* Close-Button oben rechts — die TouchableOpacity-uebergreifend funktioniert
+              wegen ZoomableImage-PanResponder nicht zuverlaessig fuer Tap-to-Close */}
+          <TouchableOpacity
+            style={{ position: 'absolute', top: 32, right: 16, padding: 12, backgroundColor: 'rgba(0,0,0,0.5)', borderRadius: 24 }}
+            onPress={() => setFullscreenImage(null)}
+          >
+            <Text style={{ color: '#FFF', fontSize: 22 }}>{'✕'}</Text>
+          </TouchableOpacity>
+        </View>
       </Modal>
 
       {/* Datei-Upload Modal */}