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/2_job-submission.md

@@ -0,0 +1,135 @@
+# Job Submission Guide
+
+Submit compute jobs to the AITBC network.
+
+## Basic Submission
+
+```bash
+aitbc client submit --model gpt2 --input data.txt --output results/
+```
+
+## Options Reference
+
+| Option | Required | Description |
+|--------|----------|-------------|
+| `--model` | Yes | Model to run (e.g., gpt2, llama, stable-diffusion) |
+| `--input` | Yes | Input file or data |
+| `--output` | Yes | Output directory |
+| `--gpu` | No | GPU requirements (v100, a100, rtx3090) |
+| `--gpu-count` | No | Number of GPUs (default: 1) |
+| `--timeout` | No | Job timeout in seconds (default: 3600) |
+| `--priority` | No | Job priority (low, normal, high) |
+
+## GPU Requirements
+
+### Single GPU
+
+```bash
+aitbc client submit --model gpt2 --input data.txt --gpu v100
+```
+
+### Multiple GPUs
+
+```bash
+aitbc client submit --model llama --input data.txt --gpu a100 --gpu-count 4
+```
+
+### Specific GPU Type
+
+```bash
+aitbc client submit --model stable-diffusion --input data.txt --gpu rtx3090
+```
+
+## Input Methods
+
+### File Input
+
+```bash
+aitbc client submit --model gpt2 --input ./data/training_data.txt
+```
+
+### Inline Input
+
+```bash
+aitbc client submit --model gpt2 --input "Hello, world!"
+```
+
+### URL Input
+
+```bash
+aitbc client submit --model gpt2 --input https://example.com/data.txt
+```
+
+## Output Options
+
+### Local Directory
+
+```bash
+aitbc client submit --model gpt2 --input data.txt --output ./results
+```
+
+### S3 Compatible Storage
+
+```bash
+aitbc client submit --model gpt2 --input data.txt --output s3://my-bucket/results
+```
+
+## Job Priority
+
+| Priority | Speed | Cost |
+|----------|-------|------|
+| low | Standard | 1x |
+| normal | Fast | 1.5x |
+| high | Priority | 2x |
+
+## Examples
+
+### Training Job
+
+```bash
+aitbc client submit \
+  --model llama \
+  --input ./training_data.csv \
+  --output ./model_weights \
+  --gpu a100 \
+  --gpu-count 4 \
+  --timeout 7200 \
+  --priority high
+```
+
+### Inference Job
+
+```bash
+aitbc client submit \
+  --model gpt2 \
+  --input ./prompts.txt \
+  --output ./outputs \
+  --gpu v100 \
+  --timeout 600
+```
+
+## Batch Jobs
+
+Submit multiple jobs at once:
+
+```bash
+# Using a job file
+aitbc client submit-batch --file jobs.yaml
+```
+
+Example `jobs.yaml`:
+
+```yaml
+jobs:
+  - model: gpt2
+    input: data1.txt
+    output: results1/
+  - model: gpt2
+    input: data2.txt
+    output: results2/
+```
+
+## Next
+
+- [3_job-lifecycle.md](./3_job-lifecycle.md) — Status, results, history, cancellation
+- [5_pricing-billing.md](./5_pricing-billing.md) — Cost structure and invoices