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/governance/governance_abi.json

@@ -0,0 +1,55 @@
+{
+  "contract": "governance",
+  "version": "1.0.0",
+  "description": "On-chain parameter governance. The deployer becomes the admin. Anyone can propose a parameter change; the admin approves or rejects it. Used to manage gas_price, messenger_entry_fee, relay_fee, etc.",
+  "methods": [
+    {
+      "name": "init",
+      "description": "Initialize the contract, setting the caller as the admin. Must be called once after deployment.",
+      "args": []
+    },
+    {
+      "name": "propose",
+      "description": "Submit a proposal to change a named parameter. Anyone can propose. Logs 'proposed: <key>=<value>'.",
+      "args": [
+        {"name": "key",   "type": "string", "description": "Parameter name (max 64 chars)"},
+        {"name": "value", "type": "string", "description": "Proposed new value (max 256 chars)"}
+      ]
+    },
+    {
+      "name": "approve",
+      "description": "Admin approves the pending proposal for a key, committing it as the live value. Logs 'approved: <key>'.",
+      "args": [
+        {"name": "key", "type": "string", "description": "Parameter key to approve"}
+      ]
+    },
+    {
+      "name": "reject",
+      "description": "Admin rejects and removes the pending proposal for a key. Logs 'rejected: <key>'.",
+      "args": [
+        {"name": "key", "type": "string", "description": "Parameter key to reject"}
+      ]
+    },
+    {
+      "name": "get",
+      "description": "Read the current live value of a parameter. Logs 'value: <value>' or 'not set: <key>'.",
+      "args": [
+        {"name": "key", "type": "string", "description": "Parameter key"}
+      ]
+    },
+    {
+      "name": "get_pending",
+      "description": "Read the pending proposed value. Logs 'pending: <value>' or 'no pending: <key>'.",
+      "args": [
+        {"name": "key", "type": "string", "description": "Parameter key"}
+      ]
+    },
+    {
+      "name": "set_admin",
+      "description": "Transfer the admin role to a new address. Only the current admin may call this. Logs 'admin: <new_admin>'.",
+      "args": [
+        {"name": "new_admin", "type": "string", "description": "New admin address (hex pubkey)"}
+      ]
+    }
+  ]
+}