[Feature] Implement Site Management API module

[talltechy]

Description

Create comprehensive Site Management module following v2.0 architecture patterns.

Features

• List sites with pagination
• Get site details
• Smart filtering (name patterns, IDs, empty sites)
• Mass delete with validation and dry-run
• Update site properties
• Search sites by criteria

Acceptance Criteria

• SiteAPI class created inheriting from BaseAPI
• All CRUD operations implemented (list, get, create, update, delete)
• Smart filtering system working:
  • Filter by name prefix/suffix (e.g., starts with 'sn_')
  • Filter by partial name match (contains)
  • Filter by site ID (single or list)
  • Filter by empty sites (no assets)
• Mass delete with preview mode (dry-run)
• Integrated with InsightVMClient as client.sites
• Unit tests added
• Documentation updated

Technical Details

• Follow BaseAPI inheritance pattern
• Use consistent error handling
• Include comprehensive docstrings
• Type hints throughout

Context

Part of Sprint 2: Site Management (4-6 hours)

This is a high-priority user-requested feature for managing large numbers of sites efficiently.

See: memory-bank/github-workflow.md for workflow details