feat: implement Call Center queues (mod_callcenter)

- Investigated the real callcenter_config command surface via
  'help callcenter_config' on the running FreeSWITCH before writing any
  code: queues only have load/unload/reload (static XML + reload, no
  'queue add' exists), while agents and tiers are fully dynamic via ESL
  commands (agent add, tier add) -- no file involved. This shapes the next
  phase (Agents/Tiers) differently from this one.
- queues table (tenant-scoped, RLS): strategy, moh/announce, wait times,
  tier rules, discard/abandoned handling, skip-agents-with-external-calls,
  recording_enabled
- packages/telephony: buildQueueXml()
- infrastructure/freeswitch: our own callcenter.conf.xml override (empties
  the vanilla static agents/tiers -- those become fully dynamic in the next
  phase) that includes callcenter_queues.conf.d/*.xml via X-PRE-PROCESS,
  same pattern as the Sofia gateway directory
- apps/api/src/queues: CRUD (POST/GET/GET:id/DELETE) using the queues.view/
  .manage permissions already in the seed
- b2bcall-fs-config (queue-sync.ts): one XML file per queue on a shared
  volume, synced via Redis pub/sub (b2bcall:queues:sync) on create/delete
  and once at boot -- same shape as trunk-sync.ts
- confirmed manually against the real FreeSWITCH, before coding the sync
  logic: 'queue load <name>' fails ('Invalid Queue not found!') for a file
  added after boot -- needs 'reloadxml' first to repopulate the in-memory
  XML tree from disk; after that, 'queue reload <name>' alone handles both
  create and update, no need to distinguish load vs reload
- verified end-to-end: created a queue (ROUND_ROBIN, maxWaitTime=120,
  discardAbandonedAfter=90), 'callcenter_config queue list' showed the
  correct values on the FreeSWITCH side; deleted it, list went back empty

docs/QUEUES.md

packages/telephony/src/index.ts

@@ -4,3 +4,4 @@ export * from "./freeswitch-provider";
 export * from "./directory-xml";
 export * from "./gateway-xml";
 export * from "./dialplan-xml";
+export * from "./queue-xml";