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.

ts/sip/index.ts

@@ -0,0 +1,16 @@
+export { SipMessage } from './message.ts';
+export { SipDialog } from './dialog.ts';
+export type { TDialogState } from './dialog.ts';
+export { rewriteSipUri, rewriteSdp } from './rewrite.ts';
+export {
+  generateCallId,
+  generateTag,
+  generateBranch,
+  codecName,
+  buildSdp,
+  parseSdpEndpoint,
+  parseDigestChallenge,
+  computeDigestAuth,
+} from './helpers.ts';
+export type { ISdpOptions, IDigestChallenge } from './helpers.ts';
+export type { IEndpoint } from './types.ts';