rework: address review feedback on PR #126

Changes per sneak's review:
- Delete docker-compose.yml, add example stanza to README
- Define custom domain types: ImageID, ContainerID, UnparsedURL
- Use custom types in all function signatures throughout codebase
- Restore imageID parameter (as domain.ImageID) in deploy pipeline
- buildContainerOptions now takes ImageID directly instead of
  constructing image tag from deploymentID
- Fix pre-existing JS formatting (prettier)

make check passes with zero failures.

internal/service/deploy/deploy_container_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"git.eeqj.de/sneak/upaas/internal/database"
+	"git.eeqj.de/sneak/upaas/internal/domain"
 	"git.eeqj.de/sneak/upaas/internal/models"
 	"git.eeqj.de/sneak/upaas/internal/service/deploy"
 )
@@ -27,14 +28,14 @@ func TestBuildContainerOptionsUsesImageID(t *testing.T) {
 	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
 	svc := deploy.NewTestService(log)
 
-	const expectedImageID = "sha256:abc123def456"
+	const expectedImageID = domain.ImageID("sha256:abc123def456")
 
 	opts, err := svc.BuildContainerOptionsExported(context.Background(), app, expectedImageID)
 	if err != nil {
 		t.Fatalf("buildContainerOptions returned error: %v", err)
 	}
 
-	if opts.Image != expectedImageID {
+	if opts.Image != string(expectedImageID) {
 		t.Errorf("expected Image=%q, got %q", expectedImageID, opts.Image)
 	}