feat: add structured output formats

[techgaun]

Summary

• add streaming text, csv, json, and jsonl result writers
• add --format selection and --output as the preferred output-file option
• preserve -o and --outputFile compatibility and their historical CSV default
• protect existing output files unless --force is provided
• add --quiet and --verbose controls
• keep structured stdout machine-readable by routing status messages to stderr
• include scan statistics in JSON and JSONL output
• keep output I/O failures fatal rather than treating them as failed GitHub queries

Output contracts

• JSON: one object containing results and summary
• JSONL: typed result records followed by one typed summary record
• CSV: retains the existing five-column header
• Text: retains the existing human-readable result layout

Safety and compatibility

github-dorks -o results.csv ... continues to select CSV automatically. It now refuses to replace an existing file; pass --force to opt into replacement.

Verification

• python3 -m unittest discover -s tests -v (24 tests)
• flake8 in Python 3.12
• git diff --check
• Docker image/package build
• installed CLI help smoke test