feat: add TLS support to Rust implementation

- Add async-native-tls dependency for secure IMAP connections
- Implement ImapStream enum supporting both TLS and plain connections
- Add automatic TLS detection based on port (993=TLS, 143=plain, 3143=test)
- Add comprehensive Read/Write trait implementations for stream wrapper
- Add debug logging for connection type verification
- Create example configurations for Gmail, Outlook, and other providers
- Add TLS_SUPPORT.md documentation with security guidelines
- Test with existing test environment and TLS detection logic
- Maintain backward compatibility with plain IMAP for testing

The Rust implementation now supports secure connections to production
email providers while maintaining compatibility with test environments.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

rust/Cargo.toml

@@ -33,6 +33,9 @@ config = "0.13"
 async-imap = "0.9"
 async-std = { version = "1.12", features = ["attributes"] }
 
+# TLS support for secure IMAP connections
+async-native-tls = "0.5"
+
 # Logging
 log = "0.4"
 env_logger = "0.10"