softphone: People panel with presence, click-to-call

People lists every extension with its status dot and a search box: a
right-hand column on wide screens, /me/people on small ones. Call uses the
browser softphone when it's on, else POST /api/me/click-to-call, which
originates to the user's desk phone first (409 if none is registered).
During a call: Transfer (blind), Talk first (consult), or drag the call
card onto a person; a held call card offers Complete transfer whenever
another call is active. useSoftphone moved to its own module.

e2e m5-t3: the dot changes ~30 ms after Asterisk's hint; click-to-call
rings 174 before 172. cdp click() takes a scope (People also has
Call/Transfer buttons). trunk-test ignores the RTCP-at-teardown EPERM
error seen once.

Task: M5-T3

scripts/e2e/README.md

@@ -69,3 +69,8 @@ directions.
 `phones.mjs` and checks the softphone features: the incoming call dialog, DTMF, hold (music on hold
 at the other end), call waiting, blind and attended transfer, and "Use here" moving the softphone to
 a second tab (`cdp.mjs` `newTab()`).
+
+`m5-t3.mjs` (after `m5-t2.mjs`) is the M5-T3 acceptance. It watches People in one browser while 173
+calls 172 and measures the time from Asterisk's hint changing to the dot changing (must be < 1 s).
+Then a second browser, as a new user with desk phone 174 and the softphone off, clicks **Call** on
+172: 174 must ring first (Asterisk channel order), then the two are connected.