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/lib/storage.ts

@@ -0,0 +1,101 @@
+/**
+ * Persistent storage for keys and app settings.
+ * On mobile: expo-secure-store for key material, AsyncStorage for settings.
+ * On web: falls back to localStorage (dev only).
+ */
+
+import * as SecureStore from 'expo-secure-store';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+import type { KeyFile, Contact, NodeSettings } from './types';
+
+// ─── Keys ─────────────────────────────────────────────────────────────────────
+
+const KEYFILE_KEY = 'dchain_keyfile';
+const CONTACTS_KEY = 'dchain_contacts';
+const SETTINGS_KEY = 'dchain_settings';
+const CHATS_KEY = 'dchain_chats';
+
+/** Save the key file in secure storage (encrypted on device). */
+export async function saveKeyFile(kf: KeyFile): Promise<void> {
+  await SecureStore.setItemAsync(KEYFILE_KEY, JSON.stringify(kf));
+}
+
+/** Load key file. Returns null if not set. */
+export async function loadKeyFile(): Promise<KeyFile | null> {
+  const raw = await SecureStore.getItemAsync(KEYFILE_KEY);
+  if (!raw) return null;
+  return JSON.parse(raw) as KeyFile;
+}
+
+/** Delete key file (logout / factory reset). */
+export async function deleteKeyFile(): Promise<void> {
+  await SecureStore.deleteItemAsync(KEYFILE_KEY);
+}
+
+// ─── Node settings ─────────────────────────────────────────────────────────────
+
+const DEFAULT_SETTINGS: NodeSettings = {
+  nodeUrl:    'http://localhost:8081',
+  contractId: '',
+};
+
+export async function loadSettings(): Promise<NodeSettings> {
+  const raw = await AsyncStorage.getItem(SETTINGS_KEY);
+  if (!raw) return DEFAULT_SETTINGS;
+  return { ...DEFAULT_SETTINGS, ...JSON.parse(raw) };
+}
+
+export async function saveSettings(s: Partial<NodeSettings>): Promise<void> {
+  const current = await loadSettings();
+  await AsyncStorage.setItem(SETTINGS_KEY, JSON.stringify({ ...current, ...s }));
+}
+
+// ─── Contacts ─────────────────────────────────────────────────────────────────
+
+export async function loadContacts(): Promise<Contact[]> {
+  const raw = await AsyncStorage.getItem(CONTACTS_KEY);
+  if (!raw) return [];
+  return JSON.parse(raw) as Contact[];
+}
+
+export async function saveContact(c: Contact): Promise<void> {
+  const contacts = await loadContacts();
+  const idx = contacts.findIndex(x => x.address === c.address);
+  if (idx >= 0) contacts[idx] = c;
+  else contacts.push(c);
+  await AsyncStorage.setItem(CONTACTS_KEY, JSON.stringify(contacts));
+}
+
+export async function deleteContact(address: string): Promise<void> {
+  const contacts = await loadContacts();
+  await AsyncStorage.setItem(
+    CONTACTS_KEY,
+    JSON.stringify(contacts.filter(c => c.address !== address)),
+  );
+}
+
+// ─── Message cache (per-chat local store) ────────────────────────────────────
+
+export interface CachedMessage {
+  id:        string;
+  from:      string;
+  text:      string;
+  timestamp: number;
+  mine:      boolean;
+}
+
+export async function loadMessages(chatId: string): Promise<CachedMessage[]> {
+  const raw = await AsyncStorage.getItem(`${CHATS_KEY}_${chatId}`);
+  if (!raw) return [];
+  return JSON.parse(raw) as CachedMessage[];
+}
+
+export async function appendMessage(chatId: string, msg: CachedMessage): Promise<void> {
+  const msgs = await loadMessages(chatId);
+  // Deduplicate by id
+  if (msgs.find(m => m.id === msg.id)) return;
+  msgs.push(msg);
+  // Keep last 500 messages per chat
+  const trimmed = msgs.slice(-500);
+  await AsyncStorage.setItem(`${CHATS_KEY}_${chatId}`, JSON.stringify(trimmed));
+}