chore: sync all changes to Gitea

- Config, docs, scripts, and backup manifests
- Submodule refs unchanged (m = modified content in submodules)

Made-with: Cursor

x402-api/.env.example

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+# thirdweb (required for x402)
+# Get secret key: https://thirdweb.com → Dashboard → Settings → API Keys
+THIRDWEB_SECRET_KEY=your-thirdweb-secret-key
+
+# Server wallet that receives payments (must be a valid address)
+SERVER_WALLET_ADDRESS=0x0000000000000000000000000000000000000000
+
+# Optional: use Chain 138 for payments (default: false = use Arbitrum Sepolia + USDC for testing)
+# Set to true only after a Chain 138 token supports ERC-2612/ERC-3009. See docs/04-configuration/CHAIN138_X402_TOKEN_SUPPORT.md
+X402_USE_CHAIN_138=false
+
+# Optional: Chain 138 RPC when X402_USE_CHAIN_138=true
+RPC_URL_138=https://rpc-http-pub.d-bis.org
+
+# Optional: server port (default 4020)
+PORT=4020