feat: activate mod_xml_curl with b2bcall-fs-config (agente.md secao 26)

- apps/freeswitch-config (b2bcall-fs-config): Fastify service implementing
  the mod_xml_curl HTTP protocol (form-encoded POST -> XML response),
  containerized, no host port published
- reactivated mod_xml_curl in FreeSWITCH, binding restricted to
  directory|dialplan only (configuration was removed after testing showed
  it firing several unnecessary HTTP round-trips at boot for module
  configs we don't need dynamic — matches agente.md's own 'don't put every
  critical config through XML Curl' guidance)
- no extensions/dialplan tables exist yet (next phases), so the service
  always answers 'not found' for now — this phase only proves the wire
  protocol works without breaking the static vanilla config fallback
- verified end-to-end: user/8888 (nowhere) -> SUBSCRIBER_ABSENT via
  fs-config; user/1000 (static vanilla extension) -> USER_NOT_REGISTERED,
  proving FreeSWITCH correctly falls through to static XML when xml_curl
  says not found
- docs/XML_CURL.md, including the not-yet-authenticated endpoint note (fine
  while it only returns not-found; needs gateway-credentials before serving
  real directory/dialplan data)

docker-compose.yml

@@ -32,6 +32,20 @@ services:
       timeout: 5s
       retries: 10
 
+  fs-config:
+    build:
+      context: .
+      dockerfile: apps/freeswitch-config/Dockerfile
+    container_name: b2bcall-fs-config
+    restart: unless-stopped
+    # Sem porta publicada: so o FreeSWITCH (mesma rede do compose) chama isto.
+    healthcheck:
+      test: ["CMD", "node", "-e", "fetch('http://localhost:8080/health').then(r => process.exit(r.ok ? 0 : 1)).catch(() => process.exit(1))"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+      start_period: 10s
+
   freeswitch:
     build:
       context: ./infrastructure/freeswitch
@@ -39,6 +53,8 @@ services:
         - freeswitch_pat
     container_name: b2bcall-freeswitch
     restart: unless-stopped
+    depends_on:
+      - fs-config
     environment:
       ESL_PASSWORD: ${ESL_PASSWORD}
     # Nenhuma porta publicada no host: SIP/RTP ainda não têm troncos reais