feat(databases): S3-compatible backup targets — offsite archives + remote restore

Phase D3. Managed databases can ship backup archives to a configured
S3-compatible destination (AWS S3, MinIO, Garage, …) while the local
copy remains intact.

- backup_targets table: owner-scoped endpoint/bucket/region/prefix +
  encrypted access/secret keys (enc:v1:, never returned, has_credentials)
- create/update probe bucket access before storing; empty keys on update
  keep stored credentials; delete refused (409) while referenced
- databases.backup_target_id assigns a target; external DBs rejected
- backup pipeline uploads via a holder container over docker cp streams;
  remote failure keeps the local archive (logged), row gets remote:true
- restore prefers the local archive; on a missing local copy it downloads
  the remote object into the backup volume first
- holder containers must be started before archive ops — docker cp does
  not resolve volume mounts on never-started (Created) containers, and
  removing the source mid-stream stalls the reader without EOF
- CLI: backup-targets list|add|update|remove|test + databases update
  --backup-target; MCP: 5 new tools; Settings UI card + per-database
  target picker + offsite badge on backups; OpenAPI + llms.txt + CLI.md

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

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

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

@@ -0,0 +1,204 @@
+package commands
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+// BackupTargetsCmd manages S3-compatible backup destinations.
+var BackupTargetsCmd = &cobra.Command{
+	Use:     "backup-targets",
+	Aliases: []string{"backup-target", "targets"},
+	Short:   "Manage S3-compatible backup targets",
+}
+
+var btListCmd = &cobra.Command{
+	Use:   "list",
+	Short: "List backup targets",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c, err := client()
+		if err != nil {
+			return err
+		}
+		data, err := c.Do("GET", "/backup-targets", nil)
+		if err != nil {
+			return err
+		}
+		items, err := unwrapList(data, "backup_targets")
+		if err != nil {
+			return err
+		}
+		rows := make([][]string, 0, len(items))
+		for _, t := range items {
+			creds := "no"
+			if str(t, "has_credentials") == "true" {
+				creds = "yes"
+			}
+			rows = append(rows, []string{str(t, "id"), str(t, "name"), str(t, "endpoint"), str(t, "bucket"), creds})
+		}
+		printRows(data, []string{"ID", "NAME", "ENDPOINT", "BUCKET", "CREDS"}, rows)
+		return nil
+	},
+}
+
+var btAddCmd = &cobra.Command{
+	Use:   "add <name>",
+	Short: "Register an S3-compatible backup target (probed before storing)",
+	Args:  cobra.ExactArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c, err := client()
+		if err != nil {
+			return err
+		}
+		body := map[string]interface{}{"name": args[0]}
+		for _, f := range []string{"endpoint", "bucket", "region", "prefix", "access-key", "secret-key"} {
+			if v, _ := cmd.Flags().GetString(f); v != "" {
+				key := f
+				switch f {
+				case "access-key":
+					key = "access_key"
+				case "secret-key":
+					key = "secret_key"
+				}
+				body[key] = v
+			}
+		}
+		if cmd.Flags().Changed("no-tls") {
+			v, _ := cmd.Flags().GetBool("no-tls")
+			body["use_tls"] = !v
+		}
+		data, err := c.Do("POST", "/backup-targets", body)
+		if err != nil {
+			return err
+		}
+		PrintRaw(data)
+		return nil
+	},
+}
+
+var btUpdateCmd = &cobra.Command{
+	Use:   "update <id>",
+	Short: "Update a backup target (re-probed; empty keys keep stored credentials)",
+	Args:  cobra.ExactArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c, err := client()
+		if err != nil {
+			return err
+		}
+		body := map[string]interface{}{}
+		// endpoint/bucket are required by the API — fall back to stored values.
+		for _, f := range []string{"name", "endpoint", "bucket", "region", "prefix", "access-key", "secret-key"} {
+			if v, _ := cmd.Flags().GetString(f); v != "" {
+				key := f
+				switch f {
+				case "access-key":
+					key = "access_key"
+				case "secret-key":
+					key = "secret_key"
+				}
+				body[key] = v
+			}
+		}
+		if _, hasEndpoint := body["endpoint"]; !hasEndpoint {
+			data, err := c.Do("GET", "/backup-targets", nil)
+			if err != nil {
+				return err
+			}
+			items, err := unwrapList(data, "backup_targets")
+			if err != nil {
+				return err
+			}
+			for _, t := range items {
+				if str(t, "id") == args[0] {
+					body["endpoint"] = str(t, "endpoint")
+					if _, ok := body["bucket"]; !ok {
+						body["bucket"] = str(t, "bucket")
+					}
+					if _, ok := body["name"]; !ok {
+						body["name"] = str(t, "name")
+					}
+					break
+				}
+			}
+		}
+		if cmd.Flags().Changed("no-tls") {
+			v, _ := cmd.Flags().GetBool("no-tls")
+			body["use_tls"] = !v
+		}
+		data, err := c.Do("PUT", "/backup-targets/"+args[0], body)
+		if err != nil {
+			return err
+		}
+		PrintRaw(data)
+		return nil
+	},
+}
+
+var btRemoveCmd = &cobra.Command{
+	Use:   "remove <id>",
+	Short: "Delete a backup target (fails while databases still point at it)",
+	Args:  cobra.ExactArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c, err := client()
+		if err != nil {
+			return err
+		}
+		if !Confirm(fmt.Sprintf("Delete backup target %s?", args[0])) {
+			return &APIError{Message: "aborted (pass --yes to skip confirmation)", ExitCode: ExitError}
+		}
+		if _, err := c.Do("DELETE", "/backup-targets/"+args[0], nil); err != nil {
+			return err
+		}
+		if JSONMode() {
+			return PrintJSON(map[string]string{"status": "deleted", "id": args[0]})
+		}
+		fmt.Printf("Deleted backup target %s\n", args[0])
+		return nil
+	},
+}
+
+var btTestCmd = &cobra.Command{
+	Use:   "test <id>",
+	Short: "Re-probe a backup target's bucket access",
+	Args:  cobra.ExactArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c, err := client()
+		if err != nil {
+			return err
+		}
+		data, err := c.Do("POST", "/backup-targets/"+args[0]+"/test", nil)
+		if err != nil {
+			return err
+		}
+		m, _ := unwrapObject(data)
+		if str(m, "ok") == "false" {
+			return &APIError{Message: "probe failed: " + str(m, "error"), ExitCode: ExitError}
+		}
+		if JSONMode() {
+			PrintRaw(data)
+			return nil
+		}
+		fmt.Printf("Target ok (%sms)\n", str(m, "latency_ms"))
+		return nil
+	},
+}
+
+func init() {
+	btAddCmd.Flags().String("endpoint", "", "S3 endpoint host[:port] (e.g. s3.amazonaws.com, garage.local:3900)")
+	btAddCmd.Flags().String("bucket", "", "bucket name")
+	btAddCmd.Flags().String("region", "", "region (optional for most S3-compatible stores)")
+	btAddCmd.Flags().String("prefix", "", "key prefix for archives")
+	btAddCmd.Flags().String("access-key", "", "access key (stored encrypted)")
+	btAddCmd.Flags().String("secret-key", "", "secret key (stored encrypted)")
+	btAddCmd.Flags().Bool("no-tls", false, "use plain HTTP")
+	btUpdateCmd.Flags().String("name", "", "new name")
+	btUpdateCmd.Flags().String("endpoint", "", "S3 endpoint host[:port]")
+	btUpdateCmd.Flags().String("bucket", "", "bucket name")
+	btUpdateCmd.Flags().String("region", "", "region")
+	btUpdateCmd.Flags().String("prefix", "", "key prefix")
+	btUpdateCmd.Flags().String("access-key", "", "access key")
+	btUpdateCmd.Flags().String("secret-key", "", "secret key")
+	btUpdateCmd.Flags().Bool("no-tls", false, "use plain HTTP")
+	BackupTargetsCmd.AddCommand(btListCmd, btAddCmd, btUpdateCmd, btRemoveCmd, btTestCmd)
+}

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

@@ -112,8 +112,12 @@ var dbUpdateCmd = &cobra.Command{
 			v, _ := cmd.Flags().GetString("backup-schedule")
 			body["backup_schedule"] = v
 		}
+		if cmd.Flags().Changed("backup-target") {
+			v, _ := cmd.Flags().GetString("backup-target")
+			body["backup_target_id"] = v
+		}
 		if len(body) == 0 {
-			return &APIError{Message: "nothing to update — pass --public/--private-style flags, --name, or --backup-schedule", ExitCode: ExitError}
+			return &APIError{Message: "nothing to update — pass --public/--private-style flags, --name, --backup-schedule, or --backup-target", ExitCode: ExitError}
 		}
 		data, err := c.Do("PUT", "/databases/"+args[0], body)
 		if err != nil {
@@ -318,6 +322,7 @@ func init() {
 	dbUpdateCmd.Flags().Bool("public", false, "bind the database port on all interfaces")
 	dbUpdateCmd.Flags().String("name", "", "rename the database")
 	dbUpdateCmd.Flags().String("backup-schedule", "", "cron expression for automatic backups (empty clears)")
+	dbUpdateCmd.Flags().String("backup-target", "", "backup target id for offsite archives (empty clears)")
 	for _, cmd := range []*cobra.Command{dbRegisterCmd, dbTestConnCmd} {
 		cmd.Flags().String("type", "postgres", "postgres|mysql|mariadb|mongodb|redis|dragonfly|clickhouse")
 		cmd.Flags().String("host", "", "database host")

app/backend/internal/cli/root.go

@@ -75,6 +75,7 @@ func init() {
 	rootCmd.AddCommand(commands.VariablesCmd)
 	rootCmd.AddCommand(commands.VolumesCmd)
 	rootCmd.AddCommand(commands.RegistriesCmd)
+	rootCmd.AddCommand(commands.BackupTargetsCmd)
 	rootCmd.AddCommand(commands.DatabasesCmd)
 	rootCmd.AddCommand(commands.CronCmd)
 	rootCmd.AddCommand(commands.TemplatesCmd)