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

vm/abi.go

@@ -0,0 +1,71 @@
+package vm
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// ABI describes the callable interface of a deployed contract.
+type ABI struct {
+	Methods []ABIMethod `json:"methods"`
+}
+
+// ABIMethod describes a single callable method.
+type ABIMethod struct {
+	Name string    `json:"name"`
+	Args []ABIArg  `json:"args"` // may be nil / empty for zero-arg methods
+}
+
+// ABIArg describes one parameter of a method.
+type ABIArg struct {
+	Name string `json:"name"`           // e.g. "amount"
+	Type string `json:"type,omitempty"` // e.g. "uint64", "string", "bytes"
+}
+
+// ParseABI deserializes an ABI from JSON.
+func ParseABI(jsonStr string) (*ABI, error) {
+	var a ABI
+	if err := json.Unmarshal([]byte(jsonStr), &a); err != nil {
+		return nil, fmt.Errorf("invalid ABI JSON: %w", err)
+	}
+	return &a, nil
+}
+
+// HasMethod returns true if the ABI declares the named method.
+func (a *ABI) HasMethod(name string) bool {
+	for _, m := range a.Methods {
+		if m.Name == name {
+			return true
+		}
+	}
+	return false
+}
+
+// Validate checks that method exists in the ABI and args_json has the right
+// number of elements. argsJSON may be empty ("" or "[]") for zero-arg methods.
+func (a *ABI) Validate(method string, argsJSON []byte) error {
+	var target *ABIMethod
+	for i := range a.Methods {
+		if a.Methods[i].Name == method {
+			target = &a.Methods[i]
+			break
+		}
+	}
+	if target == nil {
+		return fmt.Errorf("method %q not found in ABI", method)
+	}
+	if len(target.Args) == 0 {
+		return nil // no args expected — nothing to validate
+	}
+	if len(argsJSON) > 0 {
+		var args []any
+		if err := json.Unmarshal(argsJSON, &args); err != nil {
+			return fmt.Errorf("args_json is not a JSON array: %w", err)
+		}
+		if len(args) != len(target.Args) {
+			return fmt.Errorf("method %q expects %d args, got %d",
+				method, len(target.Args), len(args))
+		}
+	}
+	return nil
+}