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.go

@@ -1,22 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"mime"
-)
-
-func main() {
-	fmt.Println("🔍 MIME Type Detection Test:")
-	fmt.Println("JPG:", mime.TypeByExtension(".jpg"))
-	fmt.Println("JPEG:", mime.TypeByExtension(".jpeg"))
-	fmt.Println("PNG:", mime.TypeByExtension(".png"))
-	fmt.Println("PDF:", mime.TypeByExtension(".pdf"))
-	fmt.Println("TXT:", mime.TypeByExtension(".txt"))
-	fmt.Println("ZIP:", mime.TypeByExtension(".zip"))
-	fmt.Println("MP4:", mime.TypeByExtension(".mp4"))
-	fmt.Println("HTML:", mime.TypeByExtension(".html"))
-	fmt.Println("CSS:", mime.TypeByExtension(".css"))
-	fmt.Println("JS:", mime.TypeByExtension(".js"))
-	fmt.Println("Unknown:", mime.TypeByExtension(".xyz"))
-	fmt.Println("Empty:", mime.TypeByExtension(""))
-}