feat(nodes): SSH bootstrap + housekeeping — install script, bundled binaries, auto-prune (#50)

* feat(nodes): SSH bootstrap + housekeeping — install script, bundled binaries, auto-prune

- `containr nodes add <user@host>` mints an enroll token, SSHes once,
  runs the install script remotely; --print emits the one-liner
- Public /api/agents/install.sh + /api/agents/download/{platform};
  agent binaries built into the image under /agents
- Agent-side `prune` (bounded docker system prune, volumes opt-in)
  and `system_df` commands
- node_agents.auto_prune + health sweep enqueues daily prune;
  offline/online transitions notify admins
- CLI nodes update/prune/commands + MCP tools (prune confirm-gated)
- Usage page: install one-liner, per-node Prune + auto toggle

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat(nodes): node detail page — telemetry, containers, commands, controls

/nodes/:id (admin): cpu/mem sparklines from heartbeat history
(1h/24h/7d), containers on node, command history, inline rename,
auto-prune toggle, prune-now with volume opt-in, remove. Agent rows
on the Usage page link into it.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat(nodes): mesh awareness + node detail page

- agent reports tailscale/netbird/zerotier/wireguard interface IPs at
  register (authoritative — absent interfaces clear stored state)
- backend stores under node_agents.metadata.mesh, merged on re-register
- node detail page shows mesh addresses under the primary IP

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/mcpserver/server.go

@@ -173,6 +173,9 @@ func init() {
 	register(spec{"containr_nodes_get", "Get a node agent (admin)", "GET", "/agents/{id}", []string{"id"}, nil, false})
 	register(spec{"containr_agent_tokens_issue", "Issue an agent onboarding token (admin). Args: label.", "POST", "/agent-tokens", nil, []string{"label"}, false})
 	register(spec{"containr_agent_tokens_list", "List agent onboarding tokens (admin)", "GET", "/agent-tokens", nil, nil, false})
+	register(spec{"containr_nodes_update", "Update a node agent (admin). Args: id; optional auto_prune, name.", "PUT", "/agents/{id}", []string{"id"}, []string{"auto_prune", "name"}, false})
+	register(spec{"containr_nodes_prune", "Enqueue a bounded docker system prune on a node (admin). Args: id; optional until (e.g. 168h), volumes (danger, off by default).", "POST", "/agents/{id}/prune", []string{"id"}, []string{"until", "volumes"}, true})
+	register(spec{"containr_nodes_commands", "List recent commands sent to a node agent (admin). Args: id.", "GET", "/agents/{id}/commands", []string{"id"}, nil, false})
 
 	// Scaling / HA / security
 	register(spec{"containr_scaling_status", "Autoscaler status", "GET", "/scaling/status", nil, nil, false})