fix: lint and tests

[krakenhavoc]

This pull request focuses on improving error handling and code quality throughout the codebase, especially in test files and server shutdown logic. It also introduces a pre-commit configuration to enforce code linting and testing standards. The main themes are enhanced error checking, better resource cleanup, and improved maintainability.

Error handling improvements:

• Added error checks for os.WriteFile in multiple test cases in internal/config/config_test.go and internal/state/state_test.go, causing tests to fail if file writing fails. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
• Wrapped JSON encoding/decoding and HTTP write operations with error handling or ignored errors where appropriate to prevent unhandled errors in both application and test code (internal/health/health.go, internal/health/health_test.go, internal/reporter/reporter_test.go, internal/scanner/scanner_test.go, internal/scheduler/scheduler_test.go). [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
• Improved server shutdown logic in cmd/probe/main.go by logging errors if the health server fails to shut down cleanly.

Pre-commit hooks and code quality:

• Added a .pre-commit-config.yaml file to enforce Go linting with golangci-lint and to run tests automatically before commits, helping maintain code quality and catch issues early.