feat: add AfterCoin (AFC) private blockchain for Minecraft casino

Private Ethereum chain (Clique PoA, chain ID 8888) with ERC-20 token
(0 decimals, 1 AFC = 1 diamond) bridging casino balances on-chain so
players can view tokens in MetaMask.

- Geth v1.13.15 node with 5s block time, zero gas cost
- AfterCoin ERC-20 contract with owner-gated mint/burn/bridgeTransfer
- Bridge API (Express + ethers.js + SQLite) with register, deposit,
  withdraw, balance, and wallet endpoints
- Nonce queue for serial transaction safety
- Auto-deploys contract on first boot
- Updated mainframe Lua with diff-based on-chain sync (pcall fallback)
- Updated card generator Lua with wallet info display

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/.env.example

@@ -24,3 +24,9 @@ PUBLIC_HOST=play.yourdomain.com
 # Cloudflare API Token (create at https://dash.cloudflare.com/profile/api-tokens)
 # Permissions needed: Zone > DNS > Edit
 CF_API_TOKEN=your_cloudflare_api_token
+
+# AfterCoin Blockchain (private Ethereum chain for casino tokens)
+# Generate with: node -e "const {ethers}=require('ethers');const w=ethers.Wallet.createRandom();console.log(w.address,w.privateKey)"
+AFC_ADMIN_ADDRESS=0xYOUR_ADMIN_ADDRESS
+AFC_ADMIN_PRIVATE_KEY=your_private_key_without_0x_prefix
+AFC_BRIDGE_SECRET=change_me_in_production

docker/docker-compose.dev.yml

@@ -116,8 +116,47 @@ services:
         limits:
           memory: 8G
 
+  geth:
+    build:
+      context: ../blockchain
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    environment:
+      ADMIN_PRIVATE_KEY: ${AFC_ADMIN_PRIVATE_KEY}
+      ADMIN_ADDRESS: ${AFC_ADMIN_ADDRESS}
+    ports:
+      - "8545:8545"
+      - "8546:8546"
+    volumes:
+      - geth_data:/data
+    deploy:
+      resources:
+        limits:
+          memory: 1G
+
+  afc-bridge:
+    build:
+      context: ../services/afc-bridge
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    depends_on:
+      - geth
+    environment:
+      GETH_RPC_URL: http://geth:8545
+      ADMIN_PRIVATE_KEY: ${AFC_ADMIN_PRIVATE_KEY}
+      BRIDGE_SECRET: ${AFC_BRIDGE_SECRET}
+      PORT: 3001
+      DB_PATH: /data/bridge.db
+      GAS_FUND_AMOUNT: "0.01"
+    ports:
+      - "3001:3001"
+    volumes:
+      - afc_bridge_data:/data
+
 volumes:
   postgres_data:
   minio_data:
   openfusion_data:
   minecraft_ftb_data:
+  geth_data:
+  afc_bridge_data: