initial commit — SIP B2BUA + WebRTC bridge with Rust codec engine

Full-featured SIP router with multi-provider trunking, browser softphone
via WebRTC, real-time Opus/G.722/PCM transcoding in Rust, RNNoise ML
noise suppression, Kokoro neural TTS announcements, and a Lit-based
web dashboard with live call monitoring and REST API.

rust/Cargo.toml

@@ -0,0 +1,7 @@
+[workspace]
+members = ["crates/opus-codec", "crates/tts-engine"]
+resolver = "2"
+
+[profile.release]
+opt-level = 3
+lto = true