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/counter/main.go

@@ -0,0 +1,137 @@
+// Counter smart contract — compiles to WASM with GOOS=wasip1 GOARCH=wasm.
+//
+// Methods (exported via //go:export):
+//   - increment  — adds 1 to the stored counter
+//   - get        — logs the current value (readable via /api/contracts/{id}/state/counter)
+//   - reset      — resets counter to 0; only the first caller (owner) is allowed
+//
+// Host imports from the "env" module (see vm/host.go):
+//   - put_u64(keyPtr, keyLen, val)          — stores uint64 as 8-byte big-endian
+//   - get_u64(keyPtr, keyLen) uint64        — reads 8-byte big-endian uint64
+//   - get_caller(buf, bufLen) int32         — writes caller pub key hex into buf
+//   - get_state(kPtr,kLen,dPtr,dLen) int32  — reads raw state bytes
+//   - set_state(kPtr,kLen,vPtr,vLen)        — writes raw state bytes
+//   - log(msgPtr, msgLen)                   — emits message to node log
+//
+//go:build wasip1
+
+package main
+
+import (
+	"unsafe"
+)
+
+// ── host function imports ─────────────────────────────────────────────────────
+
+//go:wasmimport env put_u64
+func hostPutU64(keyPtr unsafe.Pointer, keyLen int32, val uint64)
+
+//go:wasmimport env get_u64
+func hostGetU64(keyPtr unsafe.Pointer, keyLen int32) uint64
+
+//go:wasmimport env get_caller
+func hostGetCaller(buf unsafe.Pointer, bufLen int32) int32
+
+//go:wasmimport env get_state
+func hostGetState(keyPtr unsafe.Pointer, keyLen int32, dstPtr unsafe.Pointer, dstLen int32) int32
+
+//go:wasmimport env set_state
+func hostSetState(keyPtr unsafe.Pointer, keyLen int32, valPtr unsafe.Pointer, valLen int32)
+
+//go:wasmimport env log
+func hostLog(msgPtr unsafe.Pointer, msgLen int32)
+
+// ── helpers ───────────────────────────────────────────────────────────────────
+
+func logMsg(s string) {
+	if len(s) == 0 {
+		return
+	}
+	b := []byte(s)
+	hostLog(unsafe.Pointer(&b[0]), int32(len(b)))
+}
+
+func putU64(key string, val uint64) {
+	b := []byte(key)
+	hostPutU64(unsafe.Pointer(&b[0]), int32(len(b)), val)
+}
+
+func getU64(key string) uint64 {
+	b := []byte(key)
+	return hostGetU64(unsafe.Pointer(&b[0]), int32(len(b)))
+}
+
+func getState(key string, dst []byte) int32 {
+	kb := []byte(key)
+	return hostGetState(unsafe.Pointer(&kb[0]), int32(len(kb)),
+		unsafe.Pointer(&dst[0]), int32(len(dst)))
+}
+
+func setState(key string, val []byte) {
+	kb := []byte(key)
+	hostSetState(unsafe.Pointer(&kb[0]), int32(len(kb)),
+		unsafe.Pointer(&val[0]), int32(len(val)))
+}
+
+func getCaller() string {
+	buf := make([]byte, 128)
+	n := hostGetCaller(unsafe.Pointer(&buf[0]), int32(len(buf)))
+	if n <= 0 {
+		return ""
+	}
+	return string(buf[:n])
+}
+
+// ── contract state keys ───────────────────────────────────────────────────────
+
+const (
+	keyCounter = "counter"
+	keyOwner   = "owner"
+)
+
+// ── exported contract methods ─────────────────────────────────────────────────
+
+//go:export increment
+func increment() {
+	val := getU64(keyCounter)
+	val++
+	putU64(keyCounter, val)
+	logMsg("incremented")
+}
+
+//go:export get
+func get() {
+	logMsg("get called")
+}
+
+//go:export reset
+func reset() {
+	caller := getCaller()
+	if caller == "" {
+		logMsg("reset: no caller")
+		return
+	}
+
+	ownerBuf := make([]byte, 128)
+	ownerLen := getState(keyOwner, ownerBuf)
+
+	if ownerLen == 0 {
+		// No owner set yet — first caller becomes the owner.
+		setState(keyOwner, []byte(caller))
+		putU64(keyCounter, 0)
+		logMsg("reset ok (owner set)")
+		return
+	}
+
+	owner := string(ownerBuf[:ownerLen])
+	if caller != owner {
+		logMsg("reset: unauthorized")
+		return
+	}
+
+	putU64(keyCounter, 0)
+	logMsg("reset ok")
+}
+
+// main is required by the Go runtime for wasip1 programs.
+func main() {}