Rename product to dockmv (container, image, module, env vars)

Container/image/service name, Go module path, CLI binary name, and
DOCKER_MIGRATE_* env vars still used the old working name; the project
is branded DockMV everywhere else (README, logo, Gitea repo).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

internal/migrate/packager.go

@@ -15,9 +15,9 @@ import (
 	"strings"
 	"time"
 
-	"github.com/arescom/docker-migrate/internal/dkr"
-	"github.com/arescom/docker-migrate/internal/job"
-	"github.com/arescom/docker-migrate/internal/spec"
+	"github.com/arescom/dockmv/internal/dkr"
+	"github.com/arescom/dockmv/internal/job"
+	"github.com/arescom/dockmv/internal/spec"
 )
 
 // PackageFormat selects how the finished package is laid out on disk.
@@ -102,7 +102,7 @@ func (p *Packager) Run(ctx context.Context, j *job.Job) (*Result, error) {
 	man := spec.Manifest{
 		FormatVersion: 1,
 		CreatedAt:     time.Now(),
-		CreatedBy:     "docker-migrate",
+		CreatedBy:     "dockmv",
 		SourceHost:    p.SourceHost,
 		Options:       opts,
 		Items:         p.Plan.Items,