contacts: caller names on desk phones while they ring (C4)

Spec 11 §6.1: sp-sub-dial-user asks /api/internal/caller-name (func_curl, 2 s at most; this
machine only, with an APP_SECRET-derived key, not logged) for the ringing user's name for the
caller, and sets it on each ringing leg (pre-dial handler, CONNECTEDLINE), never on the call, so
forwards and other members don't see someone else's contacts. Ring group/queue/number prefixes
kept. Contrack lookups never wait (cache, contactsWarm every 5 min). Proven on real Asterisk
with baresip: apps/api/test/asterisk/cnam-test.ts.

apps/api/src/contacts/callername.ts

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// Caller names on desk phones while they ring (11 §6 C4): before ringing a user's phones, the
+// dialplan asks GET /api/internal/caller-name (func_curl, 2 s at most) for that user's name for
+// the caller, and the phones show it.
+import { createHmac, timingSafeEqual } from 'node:crypto';
+
+/** The dialplan's key for the route, derived from APP_SECRET (stable across restarts). */
+export const callerNameToken = (appSecret: string) =>
+  createHmac('sha256', appSecret).update('selfphoneng caller-name').digest('hex');
+
+export const sameToken = (a: string, b: string) =>
+  a.length === b.length && timingSafeEqual(Buffer.from(a), Buffer.from(b));
+
+/**
+ * What a phone can show and the dialplan can carry: letters, digits, spaces and . ' & @ -, at
+ * most 40 characters. Nothing that Dial's options (, ^ ( ) |) or a SIP header (" < > \ ;) could
+ * read as syntax.
+ */
+export const phoneSafeName = (name: string) =>
+  name
+    .normalize('NFC')
+    .replace(/[^\p{L}\p{M}\p{N} .'&@-]+/gu, ' ')
+    .replace(/\s+/g, ' ')
+    .trim()
+    .slice(0, 40)
+    .trim();