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/_layout.tsx

@@ -0,0 +1,40 @@
+import '../global.css';
+
+import React, { useEffect } from 'react';
+import { Stack } from 'expo-router';
+import { StatusBar } from 'expo-status-bar';
+import { View } from 'react-native';
+import { SafeAreaProvider } from 'react-native-safe-area-context';
+import { loadKeyFile, loadSettings } from '@/lib/storage';
+import { setNodeUrl } from '@/lib/api';
+import { useStore } from '@/lib/store';
+
+export default function RootLayout() {
+  const setKeyFile  = useStore(s => s.setKeyFile);
+  const setSettings = useStore(s => s.setSettings);
+
+  // Bootstrap: load key + settings from storage
+  useEffect(() => {
+    (async () => {
+      const [kf, settings] = await Promise.all([loadKeyFile(), loadSettings()]);
+      if (kf) setKeyFile(kf);
+      setSettings(settings);
+      setNodeUrl(settings.nodeUrl);
+    })();
+  }, []);
+
+  return (
+    <SafeAreaProvider>
+      <View className="flex-1 bg-background">
+        <StatusBar style="light" />
+        <Stack
+          screenOptions={{
+            headerShown:   false,
+            contentStyle:  { backgroundColor: '#0b1220' },
+            animation:     'slide_from_right',
+          }}
+        />
+      </View>
+    </SafeAreaProvider>
+  );
+}