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/README.md

@@ -0,0 +1,93 @@
+# DChain Messenger — React Native Client
+
+E2E-encrypted mobile/desktop messenger built on the DChain blockchain stack.
+
+**Stack:** React Native · Expo · NativeWind (Tailwind) · TweetNaCl · Zustand
+
+## Quick Start
+
+```bash
+cd client-app
+npm install
+npx expo start          # opens Expo Dev Tools
+# Press 'i' for iOS simulator, 'a' for Android, 'w' for web
+```
+
+## Requirements
+
+- Node.js 18+
+- [Expo Go](https://expo.dev/client) on your phone (for Expo tunnel), or iOS/Android emulator
+- A running DChain node (see root README for `docker compose up --build -d`)
+
+## Project Structure
+
+```
+client-app/
+├── app/
+│   ├── _layout.tsx           # Root layout — loads keys, sets up nav
+│   ├── index.tsx             # Welcome / onboarding
+│   ├── (auth)/
+│   │   ├── create.tsx        # Generate new Ed25519 + X25519 keys
+│   │   ├── created.tsx       # Key created — export reminder
+│   │   └── import.tsx        # Import existing key.json
+│   └── (app)/
+│       ├── _layout.tsx       # Tab bar — Chats · Wallet · Settings
+│       ├── chats/
+│       │   ├── index.tsx     # Chat list with contacts
+│       │   └── [id].tsx      # Individual chat with E2E encryption
+│       ├── requests.tsx      # Incoming contact requests
+│       ├── new-contact.tsx   # Add contact by @username or address
+│       ├── wallet.tsx        # Balance + TX history + send
+│       └── settings.tsx      # Node URL, key export, profile
+├── components/ui/            # shadcn-style components (Button, Card, Input…)
+├── hooks/
+│   ├── useMessages.ts        # Poll relay inbox, decrypt messages
+│   ├── useBalance.ts         # Poll token balance
+│   └── useContacts.ts        # Load contacts + poll contact requests
+└── lib/
+    ├── api.ts                # REST client for all DChain endpoints
+    ├── crypto.ts             # NaCl box encrypt/decrypt, Ed25519 sign
+    ├── storage.ts            # SecureStore (keys) + AsyncStorage (data)
+    ├── store.ts              # Zustand global state
+    ├── types.ts              # TypeScript interfaces
+    └── utils.ts              # cn(), formatAmount(), relativeTime()
+```
+
+## Cryptography
+
+| Operation | Algorithm | Library |
+|-----------|-----------|---------|
+| Transaction signing | Ed25519 | TweetNaCl `sign` |
+| Key exchange | X25519 (Curve25519) | TweetNaCl `box` |
+| Message encryption | NaCl box (XSalsa20-Poly1305) | TweetNaCl `box` |
+| Key storage | Device secure enclave | expo-secure-store |
+
+Messages are encrypted as:
+```
+Envelope {
+  sender_pub:    <X25519 hex>   // sender's public key
+  recipient_pub: <X25519 hex>   // recipient's public key
+  nonce:         <24-byte hex>  // random per message
+  ciphertext:    <hex>          // NaCl box(plaintext, nonce, sender_priv, recipient_pub)
+}
+```
+
+## Connect to your node
+
+1. Start the DChain node: `docker compose up --build -d`
+2. Open the app → Settings → Node URL → `http://YOUR_IP:8081`
+3. If using Expo Go on physical device: your PC and phone must be on the same network, or use `npx expo start --tunnel`
+
+## Key File Format
+
+The `key.json` exported/imported by the app:
+```json
+{
+  "pub_key":     "26018d40...",   // Ed25519 public key (64 hex chars)
+  "priv_key":    "...",           // Ed25519 private key (128 hex chars)
+  "x25519_pub":  "...",           // X25519 public key (64 hex chars)
+  "x25519_priv": "..."            // X25519 private key (64 hex chars)
+}
+```
+
+This is the same format as the Go node's `--key` flag.