feat(commands): add /issue-create command for 5W1H issue creation

[kcenon]

Closes #53

Summary

• Add /issue-create command for creating well-structured GitHub issues
• Follows the 5W1H framework (What, Why, Who, When, Where, How)
• Supports --type (bug, feature, refactor, docs) and --priority (critical, high, medium, low) options
• Includes organization auto-detection and explicit --org flag support
• Consistent structure with existing /issue-work and /pr-work commands

Test Plan

• Invoke /issue-create command with project name
• Verify 5W1H template is applied to created issues
• Test --type and --priority options
• Test organization auto-detection and --org flag