feat(passbolt): add Passbolt CE stack

Password manager with GPG encryption. Uses PostgreSQL for consistency
with other stacks. Backed up alongside existing databases. Vaultwarden
kept running during migration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

passbolt/.env.example

@@ -0,0 +1,3 @@
+TRAEFIK_HOST=passbolt.example.com
+NETWORK_NAME=falcon_network
+DB_PASSWORD=change_me