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>

app/backend/internal/cli/commands/nodes_add.go

@@ -0,0 +1,214 @@
+package commands
+
+// SSH node bootstrap — one SSH session installs the agent (binary +
+// systemd + enroll token), then SSH is never needed again. SSH keys
+// stay client-side; the server only sees the resulting agent.
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"os"
+	"os/user"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/spf13/cobra"
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/agent"
+	"golang.org/x/term"
+)
+
+var (
+	nodeSSHKey   string
+	nodeSSHName  string
+	nodeSSHPrint bool
+)
+
+var nodesAddCmd = &cobra.Command{
+	Use:   "add <[user@]host[:port]>",
+	Short: "Bootstrap a node agent over SSH (one session, then closed)",
+	Long: `Installs the containr agent on a remote host:
+
+  1. mints a single-use enroll token via the API
+  2. SSHes in (agent socket, --key, or default key files)
+  3. runs the instance's install script remotely
+  4. closes the session — the agent heartbeats outbound from then on
+
+Use --print to skip SSH and emit the remote one-liner for manual runs.`,
+	Args: cobra.ExactArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c, err := client()
+		if err != nil {
+			return err
+		}
+
+		// Mint the enroll token first — SSH failures then don't leave
+		// partial state on the remote.
+		body := map[string]interface{}{"label": "bootstrap"}
+		if nodeSSHName != "" {
+			body["label"] = "bootstrap:" + nodeSSHName
+		}
+		tokenData, err := c.Do("POST", "/agent-tokens", body)
+		if err != nil {
+			return err
+		}
+		tokenObj, err := unwrapObject(tokenData, "token")
+		if err != nil {
+			return err
+		}
+		token := str(tokenObj, "token")
+		if token == "" {
+			return &APIError{Message: "enroll token missing from response", ExitCode: ExitError}
+		}
+
+		// Agent bootstrap endpoints live at /api/agents (no /v1) — strip
+		// the API version suffix off the client base.
+		apiRoot := strings.TrimSuffix(c.BaseURL, "/api/v1")
+		installCmd := fmt.Sprintf(
+			`curl -fsSL %q | bash -s -- --url %q --token %q --name %q`,
+			apiRoot+"/api/agents/install.sh", apiRoot, token, firstNonEmptyStr(nodeSSHName, nodeSSHTarget(args[0]).host),
+		)
+
+		if nodeSSHPrint {
+			fmt.Println(installCmd)
+			return nil
+		}
+
+		target := nodeSSHTarget(args[0])
+		if err := sshBootstrap(target, installCmd); err != nil {
+			return err
+		}
+		fmt.Printf("agent installing on %s — it should appear in `containr nodes list` within ~15s\n", target.host)
+		return nil
+	},
+}
+
+type sshTarget struct {
+	user string
+	host string
+	port string
+}
+
+func nodeSSHTarget(raw string) sshTarget {
+	t := sshTarget{port: "22"}
+	rest := raw
+	if at := strings.LastIndex(rest, "@"); at >= 0 {
+		t.user = rest[:at]
+		rest = rest[at+1:]
+	}
+	if colon := strings.LastIndex(rest, ":"); colon >= 0 && !strings.Contains(rest, "]") {
+		t.host, t.port = rest[:colon], rest[colon+1:]
+	} else {
+		t.host = rest
+	}
+	if t.user == "" {
+		if u, err := user.Current(); err == nil {
+			t.user = u.Username
+		}
+	}
+	return t
+}
+
+func sshAuthMethods(keyPath string) []ssh.AuthMethod {
+	var methods []ssh.AuthMethod
+
+	// ssh-agent first — matches how people actually manage keys.
+	if sock := os.Getenv("SSH_AUTH_SOCK"); sock != "" {
+		if conn, err := net.Dial("unix", sock); err == nil {
+			defer conn.Close()
+			methods = append(methods, ssh.PublicKeysCallback(agent.NewClient(conn).Signers))
+		}
+	}
+
+	var keyFiles []string
+	if keyPath != "" {
+		keyFiles = []string{keyPath}
+	} else if home, err := os.UserHomeDir(); err == nil {
+		for _, name := range []string{"id_ed25519", "id_rsa", "id_ecdsa"} {
+			p := filepath.Join(home, ".ssh", name)
+			if _, err := os.Stat(p); err == nil {
+				keyFiles = append(keyFiles, p)
+			}
+		}
+	}
+	for _, p := range keyFiles {
+		if signer, err := sshPrivateKey(p); err == nil {
+			methods = append(methods, ssh.PublicKeys(signer))
+		}
+	}
+	return methods
+}
+
+func sshPrivateKey(path string) (ssh.Signer, error) {
+	pem, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	signer, err := ssh.ParsePrivateKey(pem)
+	if err != nil {
+		var missing *ssh.PassphraseMissingError
+		if errors.As(err, &missing) {
+			fmt.Fprintf(os.Stderr, "passphrase for %s: ", path)
+			pass, readErr := term.ReadPassword(int(os.Stdin.Fd()))
+			fmt.Fprintln(os.Stderr)
+			if readErr != nil {
+				return nil, readErr
+			}
+			return ssh.ParsePrivateKeyWithPassphrase(pem, pass)
+		}
+		return nil, err
+	}
+	return signer, nil
+}
+
+func sshBootstrap(t sshTarget, remoteCmd string) error {
+	config := &ssh.ClientConfig{
+		User:            t.user,
+		Auth:            sshAuthMethods(nodeSSHKey),
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(), // jarvis: TOFU would be better; ssh_known_hosts parsing is the upgrade path
+		Timeout:         15 * time.Second,
+	}
+	if len(config.Auth) == 0 {
+		return &APIError{Message: "no SSH auth methods (ssh-agent empty, no usable keys)", ExitCode: ExitError}
+	}
+
+	conn, err := ssh.Dial("tcp", net.JoinHostPort(t.host, t.port), config)
+	if err != nil {
+		return &APIError{Message: fmt.Sprintf("ssh connect: %v", err), ExitCode: ExitError}
+	}
+	defer conn.Close()
+
+	session, err := conn.NewSession()
+	if err != nil {
+		return err
+	}
+	defer session.Close()
+	session.Stdout = os.Stdout
+	session.Stderr = os.Stderr
+
+	// Root shells run directly; otherwise escalate via sudo. NOPASSWD
+	// sudo is assumed — a password prompt here means the operator should
+	// use --print and run the command themselves.
+	if t.user == "root" {
+		return session.Run(remoteCmd)
+	}
+	return session.Run("sudo -n " + remoteCmd)
+}
+
+func firstNonEmptyStr(values ...string) string {
+	for _, v := range values {
+		if v != "" {
+			return v
+		}
+	}
+	return ""
+}
+
+func init() {
+	nodesAddCmd.Flags().StringVar(&nodeSSHKey, "key", "", "SSH private key path (defaults: agent, ~/.ssh/id_*)")
+	nodesAddCmd.Flags().StringVar(&nodeSSHName, "name", "", "node display name (defaults to remote hostname)")
+	nodesAddCmd.Flags().BoolVar(&nodeSSHPrint, "print", false, "print the remote install command instead of running SSH")
+	NodesCmd.AddCommand(nodesAddCmd)
+}