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

economy/rewards.go

@@ -0,0 +1,71 @@
+// Package economy contains helpers for computing and formatting token rewards.
+package economy
+
+import (
+	"fmt"
+
+	"go-blockchain/blockchain"
+)
+
+// BlockFeeBreakdown describes the fee income for a committed block validator.
+// There is no minting — validators earn only the fees paid by transactions.
+type BlockFeeBreakdown struct {
+	ValidatorPubKey string
+	BlockIndex      uint64
+	TxFees          uint64 // sum of all transaction fees in the block
+	IsGenesis       bool   // true for block 0 (genesis allocation, not fees)
+	GenesisAmount   uint64
+}
+
+// ComputeBlockReward calculates the fee income for a committed block.
+func ComputeBlockReward(b *blockchain.Block) BlockFeeBreakdown {
+	d := BlockFeeBreakdown{
+		ValidatorPubKey: b.Validator,
+		BlockIndex:      b.Index,
+		TxFees:          b.TotalFees,
+	}
+	if b.Index == 0 {
+		d.IsGenesis = true
+		d.GenesisAmount = blockchain.GenesisAllocation
+	}
+	return d
+}
+
+// Total returns how much the validator actually receives for this block.
+func (d BlockFeeBreakdown) Total() uint64 {
+	if d.IsGenesis {
+		return d.GenesisAmount
+	}
+	return d.TxFees
+}
+
+// Summary prints a human-readable reward summary.
+func (d BlockFeeBreakdown) Summary() string {
+	if d.IsGenesis {
+		return fmt.Sprintf(
+			"Block #0 (genesis): validator %s...%s receives genesis allocation %s",
+			d.ValidatorPubKey[:8], d.ValidatorPubKey[len(d.ValidatorPubKey)-4:],
+			FormatTokens(d.GenesisAmount),
+		)
+	}
+	if d.TxFees == 0 {
+		return fmt.Sprintf(
+			"Block #%d committed: validator %s...%s — no fees",
+			d.BlockIndex,
+			d.ValidatorPubKey[:8], d.ValidatorPubKey[len(d.ValidatorPubKey)-4:],
+		)
+	}
+	return fmt.Sprintf(
+		"Block #%d committed: validator %s...%s earns %s in fees",
+		d.BlockIndex,
+		d.ValidatorPubKey[:8], d.ValidatorPubKey[len(d.ValidatorPubKey)-4:],
+		FormatTokens(d.TxFees),
+	)
+}
+
+// FormatTokens converts micro-tokens to a human-readable string.
+func FormatTokens(microTokens uint64) string {
+	whole := microTokens / blockchain.Token
+	frac := microTokens % blockchain.Token
+	return fmt.Sprintf("%d.%06d T", whole, frac)
+}