Add whitelist/protection features

[SH20RAJ]

🎯 Goal

Allow users to protect specific paths from deletion permanently or temporarily.

🚀 Features

cleanmac --whitelist ~/Desktop/active-project
cleanmac --whitelist ~/Projects/client-work --expires 7d
cleanmac --list-whitelist
cleanmac --remove-whitelist ~/Desktop/active-project

🔧 Implementation Details

• Store whitelist in config file
• Support path patterns (wildcards)
• Support expiry dates
• Check whitelist before deletion
• Show protected items in scans

📝 Config Format

whitelist:
  - path: "~/Desktop/active-project"
    added: "2025-10-06"
    expires: null  # permanent
    reason: "Active client work"
  
  - path: "~/Projects/important-*"
    added: "2025-10-06"
    expires: "2025-10-13"
    reason: "Temporary protection"

✅ Acceptance Criteria

• Whitelisted paths are never deleted
• Expiry dates are respected
• Wildcard patterns work
• Can list all protected paths
• Can remove from whitelist

🔗 Related

Part of Phase 2