feat: add pre-commit for kai-scheduler

[rich7420]

Description

This PR adds pre-commit hooks to automatically run code quality checks before each commit, catching issues early and reducing CI failures.
Changes:
Adds .pre-commit-config.yaml with hooks for:

• General file checks (whitespace, YAML/JSON validation, large files, merge conflicts, private key detection)
• Go-specific checks (goimports formatting, go mod tidy, golangci-lint fast checks)

Adds documentation at docs/developer/pre-commit.md with installation and usage instructions
Updates CONTRIBUTING.md to reference the pre-commit documentation

Related Issues

Fixes #

Checklist

Note: Ensure your PR title follows the Conventional Commits format (e.g., feat(scheduler): add new feature)

• Self-reviewed
• Added/updated tests (if needed)
• Updated documentation (if needed)

Breaking Changes

Additional Notes