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

.gitignore

@@ -0,0 +1,44 @@
+### Env / secrets ###
+.env
+.env.*
+!.env.example
+*.pem
+*.key
+!infrastructure/**/*.example.key
+FIRST_LOGIN.txt
+
+### Node ###
+node_modules/
+dist/
+build/
+.next/
+out/
+coverage/
+*.tsbuildinfo
+npm-debug.log*
+pnpm-debug.log*
+yarn-error.log*
+
+### Docker / infra runtime data ###
+infrastructure/postgres/data/
+infrastructure/asterisk/data/
+infrastructure/asterisk/sounds/custom/
+volumes/
+
+### Logs ###
+*.log
+logs/
+
+### OS / editor ###
+.DS_Store
+.vscode/
+.idea/
+*.swp
+
+### Claude Code session data ###
+.claude/
+
+### Backups ###
+backups/*.sql
+backups/*.sql.gz
+backups/*.tar.gz