feat(rust): scaffold Rust workspace and fix TypeScript build errors

- Add @git.zone/tsrust with linux_amd64/linux_arm64 cross-compilation
- Scaffold Rust workspace with 5 crates: mailer-core, mailer-smtp, mailer-security, mailer-napi, mailer-bin
- Fix all TypeScript compilation errors for upgraded dependencies (smartfile v13, mailauth v4.13, smartproxy v23)
- Replace smartfile.fs/memory with @push.rocks/smartfs throughout codebase
- Fix .ts import extensions to .js for NodeNext module resolution
- Update DKIMSignOptions usage to match mailauth v4.13 API
- Add MTA error classes with permissive signatures for legacy SMTP client
- Replace removed DcRouter/StorageManager/deliverability imports with local interfaces

rust/Cargo.toml

@@ -0,0 +1,30 @@
+[workspace]
+resolver = "2"
+members = [
+  "crates/mailer-core",
+  "crates/mailer-smtp",
+  "crates/mailer-security",
+  "crates/mailer-napi",
+  "crates/mailer-bin",
+]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+
+[workspace.dependencies]
+tokio = { version = "1", features = ["full"] }
+tokio-rustls = "0.26"
+hickory-dns = { version = "0.25", package = "hickory-resolver" }
+mail-auth = "0.4"
+mailparse = "0.15"
+napi = { version = "2", features = ["napi9", "async", "serde-json"] }
+napi-derive = "2"
+ring = "0.17"
+dashmap = "6"
+thiserror = "2"
+tracing = "0.1"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+bytes = "1"