…r postgres issue

Fix the multiple prepare statements error with fallback

This PR adds a `--log-format` parameter to gizmosql_server that allows switching between text (default) and JSON log formats. The JSON format is optimized for ingestion by log aggregation services like Datadog.

## Changes

- Added `--log-format` parameter to gizmosql_server CLI with options: text (default), json
- Updated all logging statements to output JSON when format is set to "json"
- Maintained backward compatibility with default text format
- Applied consistent logging across both DuckDB and SQLite backends

## JSON Log Format

When using `--log-format json`, all logs are output as single-line JSON objects with:
- `level`: Log level (INFO, WARNING, ERROR)
- `message`: Human-readable message
- Additional context fields like `query`, `component`, `version`, `engine`, etc.

## Example Usage

```bash
# Default text format (backward compatible)
gizmosql_server --database-filename data.db --print-queries

# JSON format for Datadog
gizmosql_server --database-filename data.db --print-queries --log-format json
```

## Testing

- Verified both text and JSON formats work correctly
- All SQL operations tested and working
- Query logging properly outputs in JSON format when enabled
- Backward compatibility maintained

Addresses issue gizmodata#25 for consistent Arrow logging and provides foundation for structured logging requested by users for Datadog integration.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

feat: Add JSON log format support for Datadog integration

- Test workflow can run after CI build or independently
- Uses build artifacts when available, falls back to Docker
- No duplicate build logic
- Flexible setup for different environments