build: refactor codebase and improve security

[appleboy]

• Add a new .golangci.yml configuration file with a list of linters and a 3-minute timeout setting
• Refactor commit.go to improve readability by breaking long lines of flag definitions
• Replace the OpenAI client initialization in commit.go with a call to a new function NewOpenAI
• Change file permission in commit.go from 644 to 600 when writing the outputFile
• Fix a typo in an error message in hepler.go (should be helper.go)
• Create a new openai.go file to handle OpenAI client initialization
• Remove OpenAI client initialization from review.go and replace it with a call to NewOpenAI
• Refactor review.go to improve readability by breaking long lines of flag definitions
• Update error messages in git.go to remove periods at the end
• Change file permission in git.go from 755 to 600 when writing the hook file