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-config-network-resilience.toml

@@ -1,24 +0,0 @@
-# HMAC File Server Test Configuration - Network Resilience Testing
-[server]
-listen_address = "8080"
-storage_path = "./test-uploads"
-
-[security]
-secret = "test-secret-key-network-resilience-2025"
-
-[logging]
-level = "debug"
-file = "./test-server.log"
-
-[uploads]
-networkevents = true
-
-[network_resilience]
-enabled = true
-fast_detection = true
-quality_monitoring = true
-predictive_switching = true
-mobile_optimizations = true
-upload_resilience = true
-detection_interval = "1s"
-quality_check_interval = "5s"