Add full Chain 138 integration: 8 steps, chain spec, app-ethereum config, docs

Co-authored-by: Cursor <cursoragent@cursor.com>

step-03-coin-module/README.md

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+# Step 3 — Create coin module
+
+For Chain 138 we **extend the Ethereum family** in ledger-live (no new coin-module). Use:
+
+**Note:** `network-explorer.ts` uses Blockscout REST v2 API (`GET /api/v2/addresses/{address}/transactions`) with `next_page_params` pagination. Do not use Etherscan-style `module=account&action=txlist` — Blockscout uses a different API.
+
+- **config.chain138.ts** — Chain 138 RPC and explorer config; plug into Ethereum family config or currency config.
+- **network-explorer.ts** — Example network layer (getLastBlock, getBalance, getTransactionCount, getAddressTransactions). Adapt to the Ethereum coin-module’s network/bridge API (e.g. wrap in the same interface as other EVM chains).
+
+If Ledger requests a **dedicated** coin-module, create `libs/coin-modules/coin-defi_oracle_meta/` with:
+
+- `bridge/` — sync, buildTransaction, signOperation, broadcast, getFeesForTransaction, getTransactionStatus
+- `logic/` — core logic (no bridge imports)
+- `network/` — this explorer + RPC wrapper
+- `signer/` — Step 4 getAddress + sign
+- `types/` — bridge, signer, errors
+- `config.ts`, `index.ts`
+
+Dependency rule: `logic` → `network` only; `bridge` → `logic`, `network`, `signer`.