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/main.go

@@ -0,0 +1,104 @@
+// Package main is an example DChain smart contract written in Go.
+//
+// # Build
+//
+//	tinygo build -o hello_go.wasm -target wasip1 -no-debug .
+//
+// # Deploy
+//
+//	client deploy-contract --key /keys/node1.json \
+//	    --wasm hello_go.wasm --abi hello_go_abi.json \
+//	    --node http://localhost:8081
+//
+// # Use
+//
+//	client call-contract --key /keys/node1.json --contract $ID \
+//	    --method increment --gas 5000 --node http://localhost:8081
+//
+// The contract implements a simple counter with owner-gated reset.
+// It demonstrates every SDK primitive: arguments, state, caller, logging,
+// and inter-contract calls.
+package main
+
+import (
+	"strconv"
+
+	dc "go-blockchain/contracts/sdk"
+)
+
+// increment adds 1 to the counter and logs the new value.
+//
+//export increment
+func increment() {
+	v := dc.GetU64("counter")
+	v++
+	dc.PutU64("counter", v)
+	dc.Log("counter: " + strconv.FormatUint(v, 10))
+}
+
+// get logs the current counter value without changing state.
+//
+//export get
+func get() {
+	v := dc.GetU64("counter")
+	dc.Log("counter: " + strconv.FormatUint(v, 10))
+}
+
+// reset sets the counter to 0. On first call the caller becomes the owner.
+// Subsequent calls are restricted to the owner.
+//
+//export reset
+func reset() {
+	owner := dc.GetStateStr("owner")
+	caller := dc.Caller()
+	if owner == "" {
+		dc.SetStateStr("owner", caller)
+		dc.PutU64("counter", 0)
+		dc.Log("initialized — owner: " + caller[:min8(caller)])
+		return
+	}
+	if caller != owner {
+		dc.Log("unauthorized: " + caller[:min8(caller)])
+		return
+	}
+	dc.PutU64("counter", 0)
+	dc.Log("reset by owner")
+}
+
+// greet logs a personalised greeting using the first call argument.
+//
+//export greet
+func greet() {
+	name := dc.ArgStr(0, 64)
+	if name == "" {
+		name = "world"
+	}
+	dc.Log("hello, " + name + "! block=" + strconv.FormatUint(dc.BlockHeight(), 10))
+}
+
+// ping calls another contract's method (demonstrates inter-contract calls).
+// Args: contract_id (string), method (string)
+//
+//export ping
+func ping() {
+	target := dc.ArgStr(0, 64)
+	method := dc.ArgStr(1, 64)
+	if target == "" || method == "" {
+		dc.Log("ping: target and method required")
+		return
+	}
+	if dc.CallContract(target, method, "[]") {
+		dc.Log("ping: " + method + " ok")
+	} else {
+		dc.Log("ping: " + method + " failed")
+	}
+}
+
+func min8(s string) int {
+	if len(s) < 8 {
+		return len(s)
+	}
+	return 8
+}
+
+func main() {}