feat: Remove deprecated test files and enhance documentation for version 3.3.0 "Nexus Infinitum"

- Deleted obsolete test files: test_mime.go, test_mime_integration.go, and xmpp_client_upload_diagnosis.ipynb.
- Updated README.md to reflect the new version 3.3.0 "Nexus Infinitum" and its features.
- Added comprehensive release notes for version 3.3.0 detailing major enhancements and installation instructions.
- Introduced cleanup script to remove development artifacts while preserving production files.

test_mime_integration.go

@@ -1,32 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"os"
-	"path/filepath"
-)
-
-// Test the enhanced MIME type functionality
-func main() {
-	// Read the mime_types.go file to get the GetContentType function
-	fmt.Println("🔍 Testing Enhanced MIME Type Support")
-	fmt.Println("=" * 50)
-	
-	testFiles := []string{
-		"image.jpg", "document.pdf", "archive.zip", "video.mp4",
-		"audio.flac", "book.epub", "package.apk", "disk.iso",
-		"code.py", "config.toml", "font.woff2", "model.stl",
-		"database.sqlite", "backup.bak", "video.webm", "audio.opus",
-		"document.docx", "spreadsheet.xlsx", "unknown.xyz",
-	}
-	
-	// Create a simple version of the function for testing
-	for _, file := range testFiles {
-		ext := filepath.Ext(file)
-		fmt.Printf("%-20s %-10s → Enhanced MIME detection\n", file, ext)
-	}
-	
-	fmt.Println("\n✅ Enhanced MIME types will provide better content detection!")
-	fmt.Println("✅ HMAC core functions remain completely untouched!")
-	fmt.Println("✅ Backward compatibility maintained!")
-}