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

contracts/hello_go/hello_go_abi.json

@@ -0,0 +1,38 @@
+{
+  "contract": "hello_go",
+  "version": "1.0.0",
+  "description": "Example DChain contract written in Go (TinyGo SDK). Demonstrates counter, owner-gated reset, string args, and inter-contract calls.",
+  "build": "tinygo build -o hello_go.wasm -target wasip1 -no-debug .",
+  "methods": [
+    {
+      "name": "increment",
+      "description": "Add 1 to the counter. Logs 'counter: N'.",
+      "args": []
+    },
+    {
+      "name": "get",
+      "description": "Log the current counter value without changing state.",
+      "args": []
+    },
+    {
+      "name": "reset",
+      "description": "Reset counter to 0. First caller becomes the owner; only owner can reset.",
+      "args": []
+    },
+    {
+      "name": "greet",
+      "description": "Log a greeting. Logs 'hello, <name>! block=N'.",
+      "args": [
+        {"name": "name", "type": "string", "description": "Name to greet (defaults to 'world')"}
+      ]
+    },
+    {
+      "name": "ping",
+      "description": "Call a method on another contract (inter-contract call demo).",
+      "args": [
+        {"name": "contract_id", "type": "string", "description": "Target contract ID"},
+        {"name": "method",      "type": "string", "description": "Method to call on target"}
+      ]
+    }
+  ]
+}