controller v0.267.0: tests off DooPlex's Docker, cut-off copies refused, two pages true

R-650: internal/dockerexec — every docker exec routed through it; under
go test a real docker is refused (opt-in FELHOM_TEST_REAL_DOCKER=1; a stub
under the temp dir is allowed). api/stacks/web tests run under a silent
stub (TestMain). TestR650_NoBareDockerExec pins it repo-wide.
R-640: a dump without its engine's completion marker is refused before
the first mutation (unit + off-site restore) and again before any load.
R-499: the Tier-2 page's system-disk sentence has four true branches.
R-518: the backup button states the measured ~8 min stop.
R-626: measured on 9202, not reproduced.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/backup/restore.go

@@ -3,8 +3,8 @@ package backup
 import (
 	"context"
 	"fmt"
+	"gitea.dooplex.hu/admin/felhom-controller/internal/dockerexec"
 	"os"
-	"os/exec"
 	"strings"
 	"time"
 )
@@ -148,10 +148,10 @@ func (m *Manager) restoreDockerVolumesFrom(stackName, dumpDir string) (int, erro
 		m.logger.Printf("[INFO] [backup] Restoring Docker volume %s for %s", volName, stackName)
 
 		// Remove existing volume (ignore errors — may not exist)
-		exec.Command("docker", "volume", "rm", "-f", volName).Run()
+		dockerexec.Command("docker", "volume", "rm", "-f", volName).Run()
 
 		// Create fresh volume
-		if out, err := exec.Command("docker", "volume", "create", volName).CombinedOutput(); err != nil {
+		if out, err := dockerexec.Command("docker", "volume", "create", volName).CombinedOutput(); err != nil {
 			m.logger.Printf("[ERROR] [backup] Failed to create volume %s: %s — %v", volName, strings.TrimSpace(string(out)), err)
 			failed = append(failed, volName)
 			continue
@@ -159,7 +159,7 @@ func (m *Manager) restoreDockerVolumesFrom(stackName, dumpDir string) (int, erro
 
 		// Populate from tar
 		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Minute)
-		cmd := exec.CommandContext(ctx, "docker", "run", "--rm",
+		cmd := dockerexec.CommandContext(ctx, "docker", "run", "--rm",
 			"-v", volName+":/vol",
 			"-v", dumpDir+":/in:ro",
 			"alpine", "tar", "xf", "/in/"+entry.Name(), "-C", "/vol")