feat(mailer-bin): use mimalloc as the global allocator for mailer-bin

rust/crates/mailer-bin/Cargo.toml

@@ -22,3 +22,4 @@ dashmap.workspace = true
 base64.workspace = true
 uuid.workspace = true
 rustls = { version = "0.23", default-features = false, features = ["ring", "std"] }
+mimalloc = { workspace = true }

rust/crates/mailer-bin/src/main.rs

@@ -5,6 +5,9 @@
 //! 2. **Management mode** (`--management`) — JSON-over-stdin/stdout IPC for
 //!    integration with `@push.rocks/smartrust` from TypeScript
 
+#[global_allocator]
+static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;
+
 use clap::{Parser, Subcommand};
 use dashmap::DashMap;
 use serde::{Deserialize, Serialize};