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/auction/auction_abi.json

@@ -0,0 +1,45 @@
+{
+  "contract": "auction",
+  "version": "1.0.0",
+  "description": "English auction with on-chain token escrow. Bids are locked in the contract treasury. When an auction settles, the seller receives the top bid; outbid funds are automatically refunded.",
+  "methods": [
+    {
+      "name": "create",
+      "description": "Create a new auction. Logs 'created: <auction_id>'. auction_id = block_height:seq (seq auto-incremented).",
+      "args": [
+        {"name": "title",     "type": "string",  "description": "Human-readable item title (max 128 chars)"},
+        {"name": "min_bid",   "type": "uint64",  "description": "Minimum opening bid in µT"},
+        {"name": "duration",  "type": "uint64",  "description": "Duration in blocks"}
+      ]
+    },
+    {
+      "name": "bid",
+      "description": "Place a bid on an open auction. Caller transfers bid amount to the contract treasury; previous top bidder is refunded. Logs 'bid: <auction_id>'.",
+      "args": [
+        {"name": "auction_id", "type": "string", "description": "Auction ID returned by create"},
+        {"name": "amount",     "type": "uint64", "description": "Bid amount in µT (must exceed current top bid)"}
+      ]
+    },
+    {
+      "name": "settle",
+      "description": "Settle an ended auction. Transfers winning bid to seller. Anyone may call after the end block. Logs 'settled: <auction_id>'.",
+      "args": [
+        {"name": "auction_id", "type": "string", "description": "Auction ID to settle"}
+      ]
+    },
+    {
+      "name": "cancel",
+      "description": "Cancel an auction before any bids. Only the seller may cancel. Logs 'cancelled: <auction_id>'.",
+      "args": [
+        {"name": "auction_id", "type": "string", "description": "Auction ID to cancel"}
+      ]
+    },
+    {
+      "name": "info",
+      "description": "Query auction info. Logs 'seller: ...', 'title: ...', 'top_bid: ...', 'end_block: ...', 'status: open/settled/cancelled'.",
+      "args": [
+        {"name": "auction_id", "type": "string", "description": "Auction ID"}
+      ]
+    }
+  ]
+}