Implement end-of-run summary for logira run

[melonattacker]

This pull request introduces a new end-of-run summary feature for the logira run command, improving the user experience by providing concise summaries of run events and detections. It adds a --summary flag to control summary output, refactors exit code handling, and includes comprehensive tests for the new functionality.

End-of-run summary feature:

• Added run_summary.go with logic to load and render a summary of run events, detection severities, risk assessment, and top detections at the end of each run. The summary is configurable via a new --summary flag (auto, off, or detections).
• Updated run.go to parse the --summary flag, call the summary rendering function after each run, and enhance the help/usage output with new summary-related information and examples. [1] [2] [3] [4]

Exit code handling improvements:

• Added a new ExitCodeError type to cli and refactored main error handling logic to return accurate exit codes for subcommands and errors. [1] [2]

Testing:

• Added tests for the new summary logic in run_summary_test.go, verifying risk level calculation, summary rendering modes, and database seeding for test runs.
• Added tests for the new exit code handling logic in main_test.go.

Miscellaneous:

• Minor cleanup: removed an unused import in run.go.