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/3_miners/3_job-management.md

@@ -0,0 +1,96 @@
+# Job Management
+Accept and complete jobs on the AITBC network.
+
+## Overview
+
+Jobs are assigned to miners based on GPU availability, price, and reputation.
+
+## Accept Jobs
+
+### Manual Acceptance
+
+```bash
+aitbc miner jobs --available
+aitbc miner accept --job-id <JOB_ID>
+```
+
+### Auto-Accept
+
+```bash
+aitbc miner auto-accept enable --max-concurrent 4
+```
+
+### Auto-Accept Settings
+
+```bash
+# Set GPU requirements
+aitbc miner auto-accept --gpu v100 --gpu-count 1-4
+
+# Set price range
+aitbc miner auto-accept --min-price 0.08 --max-price 0.12
+```
+
+## Job States
+
+| State | Description |
+|-------|-------------|
+| assigned | Job assigned, waiting to start |
+| starting | Preparing environment |
+| running | Executing job |
+| uploading | Uploading results |
+| completed | Job finished successfully |
+| failed | Job error occurred |
+
+## Monitor Jobs
+
+### Check Status
+
+```bash
+aitbc miner job-status --job-id <JOB_ID>
+```
+
+### Watch Progress
+
+```bash
+aitbc miner watch --job-id <JOB_ID>
+```
+
+### List Active Jobs
+
+```bash
+aitbc miner jobs --active
+```
+
+## Complete Jobs
+
+### Manual Completion
+
+```bash
+aitbc miner complete --job-id <JOB_ID>
+```
+
+### Upload Results
+
+```bash
+aitbc miner upload --job-id <JOB_ID> --path ./results
+```
+
+## Handle Failures
+
+### Retry Job
+
+```bash
+aitbc miner retry --job-id <JOB_ID>
+```
+
+### Report Issue
+
+```bash
+aitbc miner report --job-id <JOB_ID> --reason "gpu-error"
+```
+
+## Next
+
+- [Earnings](./4_earnings.md) — Earnings tracking
+- [GPU Setup](./5_gpu-setup.md) — GPU configuration
+- [Monitoring](./6_monitoring.md) - Monitor your miner