[Phase 3] Implement .NET Framework IHttpModule for context initialization

[marioarce]

Task

Implement IHttpModule for .NET Framework to initialize context on BeginRequest.

Deliverables

• Implement SitecoreHttpModule:
  • Implements IHttpModule
  • Registers on BeginRequest event
  • Captures HttpContext.Current
  • Captures Sitecore.Context.Database via reflection
  • Stores in CallContext via SitecoreThreadSafeContext
• Add Web.config transformation example
• Test with Sitecore 10.4 on .NET Framework 4.8
• Add integration tests

Acceptance Criteria

• HTTP module initializes context correctly
• Context is available throughout request lifecycle
• Works with Sitecore 10.4
• Integration tests pass
• Web.config example documented