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.json

@@ -0,0 +1,36 @@
+{
+  "expo": {
+    "name": "DChain Messenger",
+    "slug": "dchain-messenger",
+    "version": "1.0.0",
+    "orientation": "portrait",
+    "userInterfaceStyle": "dark",
+    "backgroundColor": "#0d1117",
+    "ios": {
+      "supportsTablet": false,
+      "bundleIdentifier": "com.dchain.messenger"
+    },
+    "android": {
+      "package": "com.dchain.messenger",
+      "softwareKeyboardLayoutMode": "pan"
+    },
+    "web": {
+      "bundler": "metro",
+      "output": "static"
+    },
+    "plugins": [
+      "expo-router",
+      "expo-secure-store",
+      [
+        "expo-camera",
+        {
+          "cameraPermission": "Allow DChain to scan QR codes for node configuration."
+        }
+      ]
+    ],
+    "experiments": {
+      "typedRoutes": false
+    },
+    "scheme": "dchain"
+  }
+}