add(domain): fully integrate management domain

[ktwu01]

Summary

• Add Management as the 9th domain with 10 subdomains: Strategic Management, Organizational Behavior, Human Resource Management, Operations Management, Marketing, Entrepreneurship, Innovation and Technology Management, Supply Chain Management, Project Management, General Management
• Update all validation, onboarding, and UI systems to support the new domain
• Addresses community request for a management research domain

Files changed

• utils/SKILL_SCHEMA.md — add management to valid domain enum
• .github/workflows/onboard-maintainer.yml — add to folderMap and colorMap
• .github/ISSUE_TEMPLATE/02-skill-request.yml — add management subdomains to dropdown
• .github/ISSUE_TEMPLATE/03-maintainer-application.yml — add management subdomains to checkboxes
• .github/CODEOWNERS — add management reviewer placeholder
• docs/index.html — add to knowledge tree with hover descriptions
• readme.md — update to 9 domains, 165 subcategories

Test plan

• Verify management subdomains appear in skill request issue template
• Verify management subdomains appear in maintainer application issue template
• Verify knowledge tree renders management domain at https://scienceintelligence.github.io/ResearchSkills/
• Verify onboarding workflow accepts Management domain applications

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