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/2_registration.md

@@ -0,0 +1,80 @@
+# Miner Registration
+Register your miner with the AITBC network.
+
+## Requirements
+
+### Hardware Requirements
+
+| Resource | Minimum | Recommended |
+|----------|---------|-------------|
+| GPU VRAM | 8GB | 16GB+ |
+| RAM | 16GB | 32GB+ |
+| Storage | 50GB | 100GB+ |
+| Bandwidth | 10 Mbps | 100 Mbps |
+
+### Supported GPUs
+
+- NVIDIA V100 (16GB/32GB)
+- NVIDIA A100 (40GB/80GB)
+- NVIDIA RTX 3090 (24GB)
+- NVIDIA RTX 4090 (24GB)
+
+## Registration
+
+### Basic Registration
+
+```bash
+aitbc miner register --name my-miner --gpu v100 --count 1
+```
+
+### Advanced Registration
+
+```bash
+aitbc miner register \
+  --name my-miner \
+  --gpu a100 \
+  --count 4 \
+  --location us-east \
+  --price 0.10 \
+  --max-concurrent 4
+```
+
+### Flags Reference
+
+| Flag | Description |
+|------|-------------|
+| `--name` | Miner name |
+| `--gpu` | GPU type (v100, a100, rtx3090, rtx4090) |
+| `--count` | Number of GPUs |
+| `--location` | Geographic location |
+| `--price` | Price per GPU/hour in AITBC |
+| `--max-concurrent` | Maximum concurrent jobs |
+
+## Verification
+
+```bash
+aitbc miner status
+```
+
+Shows:
+- Registration status
+- GPU availability
+- Current jobs
+
+## Update Registration
+
+```bash
+aitbc miner update --price 0.12 --max-concurrent 8
+```
+
+## De-register
+
+```bash
+aitbc miner deregister --confirm
+```
+
+## Next
+
+- [Job Management](./3_job-management.md) — Job management
+- [Earnings](./4_earnings.md) — Earnings tracking
+- [GPU Setup](./5_gpu-setup.md) — GPU configuration