feat(chat): integrate chat project into monorepo with full app structure

- Restructure chat as apps/mobile, apps/web, apps/landing, backend
- Add NestJS backend for secure Azure OpenAI API calls
- Remove exposed API key from mobile app (security fix)
- Add shared chat-types package
- Create SvelteKit web app scaffold
- Create Astro landing page scaffold
- Update pnpm workspace configuration
- Add project-level CLAUDE.md documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

chat/apps/mobile/components/NewChatButton.tsx

@@ -0,0 +1,46 @@
+import React from 'react';
+import { TouchableOpacity, Text, StyleSheet } from 'react-native';
+import { Ionicons } from '@expo/vector-icons';
+import { useTheme } from '@react-navigation/native';
+
+type NewChatButtonProps = {
+  onPress: () => void;
+};
+
+export default function NewChatButton({ onPress }: NewChatButtonProps) {
+  const { colors } = useTheme();
+
+  return (
+    <TouchableOpacity 
+      style={[styles.button, { backgroundColor: colors.primary }]} 
+      onPress={onPress}
+    >
+      <Ionicons name="add" size={24} color="#fff" style={styles.icon} />
+      <Text style={styles.text}>Neuer Chat</Text>
+    </TouchableOpacity>
+  );
+}
+
+const styles = StyleSheet.create({
+  button: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    justifyContent: 'center',
+    paddingVertical: 14,
+    paddingHorizontal: 24,
+    borderRadius: 30,
+    shadowColor: '#000',
+    shadowOffset: { width: 0, height: 2 },
+    shadowOpacity: 0.1,
+    shadowRadius: 4,
+    elevation: 3,
+  },
+  icon: {
+    marginRight: 8,
+  },
+  text: {
+    color: '#fff',
+    fontSize: 16,
+    fontWeight: '600',
+  },
+});