feat(rust-proxy-engine): add a Rust SIP proxy engine with shared SIP and codec libraries

rust/crates/sip-proto/src/lib.rs

@@ -0,0 +1,17 @@
+//! SIP protocol library for the proxy engine.
+//!
+//! Provides SIP message parsing/serialization, dialog state management,
+//! SDP handling, Digest authentication, and URI rewriting.
+//! Ported from the TypeScript `ts/sip/` library.
+
+pub mod message;
+pub mod dialog;
+pub mod helpers;
+pub mod rewrite;
+
+/// Network endpoint (address + port).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Endpoint {
+    pub address: String,
+    pub port: u16,
+}