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

testdata/node2.json

@@ -0,0 +1,6 @@
+{
+  "pub_key": "bf3628d1a10fcf5a90d2cb31f387c8d1f2dac6a2c54c736c27d5ea04af9696a2",
+  "priv_key": "8289b3e36db67fe78bc7bb359590536188b084c4b302f6021bd59e7db21e543abf3628d1a10fcf5a90d2cb31f387c8d1f2dac6a2c54c736c27d5ea04af9696a2",
+  "x25519_pub": "9b7c5f43c79217dff8413ab2116b84b19b1e05606c143a82885609e08ac28579",
+  "x25519_priv": "b04fd2c99dda64e70601de5c92d05afe560733665867f911dd725ec674137a7a"
+}