Initial commit: TutaBridge IMAP/SMTP bridge for Tuta

Local bridge that exposes Tuta encrypted email via standard
IMAP/SMTP protocols for use with Thunderbird and other clients.

Features:
- IMAP server with TLS (STARTTLS self-signed cert)
- SMTP server for sending mail via Tuta
- Session persistence via macOS Keychain
- Mail body decryption including LZ4-compressed blobs
- Blob storage access (BlobAccessTokenService + blob server)
- RFC 2822 message formatting
- Interactive first-run configuration

src/main.rs

@@ -0,0 +1,52 @@
+mod config;
+mod tuta;
+mod imap;
+mod mail;
+mod smtp;
+mod tls;
+
+use std::sync::Arc;
+use log::info;
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    tokio_rustls::rustls::crypto::ring::default_provider()
+        .install_default()
+        .map_err(|_| anyhow::anyhow!("Failed to install TLS crypto provider"))?;
+
+    env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("info")).init();
+
+    let cfg = config::load_or_create_config().map_err(|e| anyhow::anyhow!("{e}"))?;
+    info!("TutaBridge starting...");
+
+    let tls_acceptor = tls::load_or_create_tls_acceptor()
+        .map_err(|e| anyhow::anyhow!("TLS setup failed: {e}"))?;
+    info!("TLS initialized");
+
+    info!("IMAP will listen on 127.0.0.1:{}", cfg.imap_port);
+    info!("SMTP will listen on 127.0.0.1:{}", cfg.smtp_port);
+
+    let session = tuta::login(&cfg).await.map_err(|e| anyhow::anyhow!("{e}"))?;
+    let session: Arc<dyn tuta::MailBackend> = Arc::new(session);
+    info!("Logged in as {}", cfg.email);
+
+    let imap_session = session.clone();
+    let smtp_session = session.clone();
+    let imap_tls = tls_acceptor.clone();
+    let smtp_tls = tls_acceptor;
+
+    let imap_handle = tokio::spawn(imap::serve(cfg.imap_port, imap_session, imap_tls));
+    let smtp_handle = tokio::spawn(smtp::serve(cfg.smtp_port, smtp_session, smtp_tls));
+
+    info!("Bridge is running. Configure Thunderbird with:");
+    info!("  IMAP server: 127.0.0.1:{} (SSL/TLS)", cfg.imap_port);
+    info!("  SMTP server: 127.0.0.1:{} (SSL/TLS)", cfg.smtp_port);
+    info!("  Username: {}", cfg.email);
+    info!("  Password: (any password — bridge handles auth)");
+    info!("  Accept the self-signed certificate when prompted");
+
+    tokio::select! {
+        r = imap_handle => r.map_err(|e| anyhow::anyhow!("{e}"))?.map_err(|e| anyhow::anyhow!("{e}")),
+        r = smtp_handle => r.map_err(|e| anyhow::anyhow!("{e}"))?.map_err(|e| anyhow::anyhow!("{e}")),
+    }
+}