chore: initial commit for v0.0.1

DChain single-node blockchain + React Native messenger client.

Core:
- PBFT consensus with multi-sig validator admission + equivocation slashing
- BadgerDB + schema migration scaffold (CurrentSchemaVersion=0)
- libp2p gossipsub (tx/v1, blocks/v1, relay/v1, version/v1)
- Native Go contracts (username_registry) alongside WASM (wazero)
- WebSocket gateway with topic-based fanout + Ed25519-nonce auth
- Relay mailbox with NaCl envelope encryption (X25519 + Ed25519)
- Prometheus /metrics, per-IP rate limit, body-size cap

Deployment:
- Single-node compose (deploy/single/) with Caddy TLS + optional Prometheus
- 3-node dev compose (docker-compose.yml) with mocked internet topology
- 3-validator prod compose (deploy/prod/) for federation
- Auto-update from Gitea via /api/update-check + systemd timer
- Build-time version injection (ldflags → node --version)
- UI / Swagger toggle flags (DCHAIN_DISABLE_UI, DCHAIN_DISABLE_SWAGGER)

Client (client-app/):
- Expo / React Native / NativeWind
- E2E NaCl encryption, typing indicator, contact requests
- Auto-discovery of canonical contracts, chain_id aware, WS reconnect on node switch

Documentation:
- README.md, CHANGELOG.md, CONTEXT.md
- deploy/single/README.md with 6 operator scenarios
- deploy/UPDATE_STRATEGY.md with 4-layer forward-compat design
- docs/contracts/*.md per contract

client-app/app/(auth)/created.tsx

@@ -0,0 +1,118 @@
+/**
+ * Account Created confirmation screen.
+ * Shows address, pubkeys, and export options.
+ */
+
+import React, { useState } from 'react';
+import { View, Text, ScrollView, Alert, Share } from 'react-native';
+import { router } from 'expo-router';
+import * as Clipboard from 'expo-clipboard';
+import * as FileSystem from 'expo-file-system';
+import * as Sharing from 'expo-sharing';
+import { useStore } from '@/lib/store';
+import { shortAddr } from '@/lib/crypto';
+import { Button } from '@/components/ui/Button';
+import { Card } from '@/components/ui/Card';
+import { Separator } from '@/components/ui/Separator';
+
+export default function AccountCreatedScreen() {
+  const keyFile = useStore(s => s.keyFile);
+  const [copied, setCopied] = useState<string | null>(null);
+
+  if (!keyFile) {
+    router.replace('/');
+    return null;
+  }
+
+  async function copy(value: string, label: string) {
+    await Clipboard.setStringAsync(value);
+    setCopied(label);
+    setTimeout(() => setCopied(null), 2000);
+  }
+
+  async function exportKey() {
+    try {
+      const json = JSON.stringify(keyFile, null, 2);
+      const path = FileSystem.cacheDirectory + 'dchain_key.json';
+      await FileSystem.writeAsStringAsync(path, json);
+      if (await Sharing.isAvailableAsync()) {
+        await Sharing.shareAsync(path, {
+          mimeType: 'application/json',
+          dialogTitle: 'Save your DChain key file',
+        });
+      } else {
+        Alert.alert('Export', 'Sharing not available on this device.');
+      }
+    } catch (e: any) {
+      Alert.alert('Export failed', e.message);
+    }
+  }
+
+  return (
+    <ScrollView
+      className="flex-1 bg-background"
+      contentContainerClassName="px-6 pt-16 pb-10"
+    >
+      {/* Success header */}
+      <View className="items-center mb-8">
+        <View className="w-20 h-20 rounded-full bg-success/20 items-center justify-center mb-4">
+          <Text className="text-4xl">✓</Text>
+        </View>
+        <Text className="text-white text-2xl font-bold">Account Created!</Text>
+        <Text className="text-muted text-sm mt-2 text-center">
+          Your keys have been generated and stored securely.
+        </Text>
+      </View>
+
+      {/* Address card */}
+      <Card className="mb-4">
+        <Text className="text-muted text-xs uppercase tracking-widest mb-3 font-semibold">
+          Your Address (Ed25519)
+        </Text>
+        <Text className="text-white font-mono text-xs leading-5 mb-3">
+          {keyFile.pub_key}
+        </Text>
+        <Button
+          variant="secondary"
+          size="sm"
+          onPress={() => copy(keyFile.pub_key, 'address')}
+        >
+          {copied === 'address' ? '✓ Copied' : 'Copy Address'}
+        </Button>
+      </Card>
+
+      {/* X25519 key */}
+      <Card className="mb-4">
+        <Text className="text-muted text-xs uppercase tracking-widest mb-3 font-semibold">
+          Encryption Key (X25519)
+        </Text>
+        <Text className="text-white font-mono text-xs leading-5 mb-3">
+          {keyFile.x25519_pub}
+        </Text>
+        <Button
+          variant="secondary"
+          size="sm"
+          onPress={() => copy(keyFile.x25519_pub, 'x25519')}
+        >
+          {copied === 'x25519' ? '✓ Copied' : 'Copy Encryption Key'}
+        </Button>
+      </Card>
+
+      {/* Export warning */}
+      <Card className="mb-8 border-yellow-500/30 bg-yellow-500/10">
+        <Text className="text-yellow-400 text-sm font-semibold mb-2">🔐 Backup your key file</Text>
+        <Text className="text-muted text-xs leading-5 mb-3">
+          Export <Text className="text-white font-mono">dchain_key.json</Text> and store it safely.
+          This file contains your private keys — keep it secret.
+        </Text>
+        <Button variant="outline" onPress={exportKey}>
+          Export key.json
+        </Button>
+      </Card>
+
+      <Button size="lg" onPress={() => router.replace('/(app)/chats')}>
+        Open Messenger
+      </Button>
+    </ScrollView>
+  );
+}