chore(mobile): restore German umlauts + ellipsis in call screen labels

The Phase-3 implementer ASCII'd four strings to side-step a Windows
console encoding issue during the apply step. The TypeScript / Metro
toolchain handles non-ASCII string literals cleanly — the workaround
was unnecessary and produced ugly UI labels ("Anruf lauft", "Hoerer",
"Verbinde ..."). Restore the originals.

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

apps/mobile/app/(app)/call.tsx

@@ -50,13 +50,13 @@ export default function CallScreen() {
   return (
     <View style={styles.container}>
       <View style={styles.header}>
-        <Text style={styles.title}>{connecting ? 'Verbinde ...' : 'Anruf lauft'}</Text>
+        <Text style={styles.title}>{connecting ? 'Verbinde …' : 'Anruf läuft'}</Text>
         {state.kind === 'connected' && <Text style={styles.duration}>{duration}</Text>}
       </View>
 
       <View style={styles.participantList}>
         {participants.length === 0 && (
-          <Text style={styles.empty}>Warten auf Teilnehmer ...</Text>
+          <Text style={styles.empty}>Warten auf Teilnehmer …</Text>
         )}
         {participants.map((p) => (
           <View key={p.identity} style={styles.participantRow}>
@@ -64,7 +64,7 @@ export default function CallScreen() {
             <View style={styles.participantText}>
               <Text style={styles.participantName}>{p.name}</Text>
               <Text style={[styles.participantStatus, p.speaking && styles.participantSpeaking]}>
-                {p.speaking ? 'Spricht ...' : 'Stumm'}
+                {p.speaking ? 'Spricht …' : 'Stumm'}
               </Text>
             </View>
           </View>
@@ -80,7 +80,7 @@ export default function CallScreen() {
           }}
         />
         <ToolbarButton
-          label={speakerOn ? 'Lautsprecher' : 'Hoerer'}
+          label={speakerOn ? 'Lautsprecher' : 'Hörer'}
           active={speakerOn}
           onPress={() => {
             void toggleSpeaker();