feat: bootstrap b2bcall architecture

- docs/ARCHITECTURE.md: decisoes de arquitetura (monorepo, rede Asterisk host
  mode, realtime PJSIP, camada de telefonia, seguranca desde o design)
- TODO.md: checklist vivo de implementacao por fases
- estrutura inicial do monorepo (apps/, packages/, infrastructure/, scripts/)
- docker-compose.yml: postgres 17 + redis 7 com healthchecks, sem portas
  publicadas no host, schema 'asterisk' dedicado no Postgres
- .env.example + scripts/generate-secrets.sh

scripts/generate-secrets.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# Gera valores fortes para os segredos do .env.
+# Uso: ./scripts/generate-secrets.sh   (imprime pares KEY=VALUE para colar no .env)
+set -euo pipefail
+
+rand_hex() { openssl rand -hex "${1:-32}"; }
+rand_b64() { openssl rand -base64 "${1:-32}"; }
+
+echo "POSTGRES_PASSWORD=$(rand_hex 24)"
+echo "REDIS_PASSWORD=$(rand_hex 24)"
+echo "JWT_ACCESS_SECRET=$(rand_hex 64)"
+echo "JWT_REFRESH_SECRET=$(rand_hex 64)"
+echo "SECRETS_MASTER_KEY=$(rand_b64 32)"
+echo "AMI_SECRET=$(rand_hex 24)"
+echo "ARI_SECRET=$(rand_hex 24)"