feat: port pneumatube to Rust on fumi-core

Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "pneumatube"
+version = "0.1.0"
+edition = "2021"
+description = "Gateway bridging a smolmail account and an SMTP mailbox"
+license = "Apache-2.0"
+
+[dependencies]
+# The smolmail protocol lives here: Noise_NX transport, sealed mail, accept
+# tokens, the local store. A sibling checkout is expected at ../fumi, the
+# same convention the deployment tooling documents.
+fumi-core = { path = "../fumi/core" }
+mail-parser = "0.11"
+rustls = { version = "0.23", default-features = false, features = ["ring", "std", "tls12", "logging"] }
+rustls-native-certs = "0.8"
+webpki-roots = "1"
+data-encoding = "2"
+
+[profile.release]
+lto = true