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-startup.toml

@@ -1,42 +0,0 @@
-[server]
-listen_address = "8080"
-storage_path = "./test-uploads"
-file_ttl = "24h"
-max_file_size_mb = 100
-metrics_enabled = true
-metrics_port = 9090
-network_events = true
-file_naming = "original"
-min_free_bytes = "1GB"
-global_extensions = [".txt", ".dat", ".log", ".json"]
-
-[server.permissions]
-storage_directory = "0755"
-
-[server.interface]
-trusted_networks = ["127.0.0.1/32", "::1/128", "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16"]
-
-[security]
-secret = "supersecret-hmac-key-minimum-16-chars"
-secret_rotation_interval = "30d"
-
-[logging]
-level = "info"
-file = "./test-server.log"
-
-[network_resilience]
-enabled = true
-detection_threshold_ms = 1000
-max_retry_attempts = 3
-backoff_multiplier = 2.0
-max_backoff_ms = 30000
-quality_threshold = 0.7
-prediction_window_ms = 5000
-
-[client_network_support]
-enabled = true
-multi_interface_detection = true
-mobile_optimization = true
-wlan_5g_switching = true
-connection_quality_monitoring = true
-adaptive_timeout_adjustment = true