chore: standardize configuration, logging, and error handling across blockchain node and coordinator API

- Add infrastructure.md and workflow files to .gitignore to prevent sensitive info leaks
- Change blockchain node mempool backend default from memory to database for persistence
- Refactor blockchain node logger with StructuredLogFormatter and AuditLogger (consistent with coordinator)
- Add structured logging fields: service, module, function, line number
- Unify coordinator config with Database

docs/2_clients/4_wallet.md

@@ -0,0 +1,78 @@
+# Wallet Management
+
+Manage your AITBC wallet and tokens.
+
+## Create Wallet
+
+```bash
+aitbc wallet create --name my-wallet
+```
+
+Save the seed phrase securely!
+
+## Import Wallet
+
+```bash
+aitbc wallet import --seed "your seed phrase words"
+```
+
+## View Balance
+
+```bash
+aitbc wallet balance
+```
+
+### Detailed Balance
+
+```bash
+aitbc wallet balance --detailed
+```
+
+Shows:
+- Available balance
+- Pending transactions
+- Locked tokens
+
+## Send Tokens
+
+```bash
+aitbc wallet send --to <ADDRESS> --amount 100
+```
+
+### With Memo
+
+```bash
+aitbc wallet send --to <ADDRESS> --amount 100 --memo "Payment for job"
+```
+
+## Transaction History
+
+```bash
+aitbc wallet history
+```
+
+### Filter
+
+```bash
+aitbc wallet history --type sent
+aitbc wallet history --type received
+```
+
+## Security
+
+### Backup Wallet
+
+```bash
+aitbc wallet export --output wallet.json
+```
+
+### Change Password
+
+```bash
+aitbc wallet change-password
+```
+
+## Next
+
+- [5_pricing-billing.md](./5_pricing-billing.md) — Cost structure and invoices
+- [CLI Guide](../0_getting_started/3_cli.md) — Full CLI reference