paging: paging groups, *80 intercom, auto-answer headers

/api/paging-groups CRUD (members as memberIds). The generator renders
sp-page-{id} per 03 §6.11 (desk phones only, auto-answer headers via
sp-sub-autoanswer) plus the number in sp-local-numbers. Added the `s`
option so phones already on a call aren't paged, which also keeps a
pager who is a member from being paged themselves. A group with no
members just hangs up.

*80<ext> intercom checks the target first: digits only and an endpoint
in sp-from-ext, else ss-noservice (the spec's one-liner passed
${EXTEN:3} straight into Page()). Both written back into 03.

Web: Paging page (list, drawer form with member checkboxes). Golden
case paging. e2e m8-t4 with baresip phones that honor the headers
(sip_autoanswer): an ordinary call rings, a page is answered by itself
and muted, the busy pager is skipped, *80 is two-way, *80999 refused.
The check on a real Yealink/Grandstream stays open (09).

Task: M8-T4

apps/api/src/generator/dialplan/static.ts

@@ -89,7 +89,7 @@ exten => _X!,1,Answer()                ; X! also matches "0" (caller unknown)
  same => n,SayDigits(\${EXTEN})
  same => n,Hangup()
 
-; ─── Feature codes (03 §6.13). Intercom *80 arrives with M8-T4.
+; ─── Feature codes (03 §6.13).
 [sp-featurecodes]
 exten => *97,1,Answer()                                     ; my voicemail
  same => n,VoiceMailMain(\${SP_EXT}@default)
@@ -150,6 +150,14 @@ exten => _*45X.,1,Answer()                                  ; *45<queue> toggle
  same => n,Hangup()
  same => n(deny),Playback(ss-noservice)
  same => n,Hangup()
+exten => _*80X.,1,Set(T=\${FILTER(0-9,\${EXTEN:3})})            ; *80<ext> intercom, both ways
+ same => n,GotoIf($["\${T}" != "\${EXTEN:3}"]?deny)
+ same => n,GotoIf($["\${PJSIP_ENDPOINT(\${T},context)}" != "sp-from-ext"]?deny)   ; desk phones only
+ same => n,Page(PJSIP/\${T},db(sp-sub-autoanswer^s^1),30)
+ same => n,Hangup()
+ same => n(deny),Answer()
+ same => n,Playback(ss-noservice)
+ same => n,Hangup()
 ; time condition overrides *31N open, *32N closed, *33N auto (admins only)
 exten => _*3[123]X,1,Answer()
  same => n,GotoIf($["\${GLOBAL(SP_TCADMIN_\${SP_EXT})}" != "1"]?deny)