feat: add pulsenode stack

Infrastructure dashboard monitoring all the stacks in this repo, built
via stacks new pulsenode and then hand-adjusted for what a generic
scaffold can't know: pulls the published image
(dev.pivoine.art/valknar/pulsenode:latest) instead of building, mounts
/var/run/docker.sock:ro plus its own config/ directory read-only, runs
read-only/non-root/cap-dropped (group_add on DOCKER_GID to get socket
access without running as root), and uses its own healthcheck.mjs
rather than curl (not present in its minimal image).

config/config.yml is real, not a placeholder: docker/database widgets
for every container across all ten stacks here, discovery enabled
against falcon_network as a safety net for anything added later.

README.md

@@ -18,6 +18,7 @@ Each stack is independently deployable with its own `compose.yml` and `.env`. Al
 | `passbolt` | Password manager (GPG-encrypted, team sharing) | passbolt, db |
 | `code` | Browser-based VS Code IDE with Anthropic API access | code |
 | `headscale` | Self-hosted Tailscale control server (WireGuard mesh VPN) | headscale |
+| `pulsenode` | Infrastructure dashboard - monitors all the stacks above | pulsenode |
 
 ## Config files