feat(migrate): containr migrate railway — GraphQL import of services/vars/domains

--token (or RAILWAY_TOKEN) reads the Railway project via backboard
GraphQL: services resolve to git-repo or image services with command +
replicas, variables and service/custom domains follow. --dry-run prints
the plan; --into targets an existing project. Both account (Bearer) and
project tokens (Project-Access-Token header) work.

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

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

@@ -0,0 +1,40 @@
+package commands
+
+import "testing"
+
+func TestRailwayRepoURL(t *testing.T) {
+	cases := map[string]string{
+		"owner/repo":             "https://github.com/owner/repo",
+		"https://gitlab.com/a/b": "https://gitlab.com/a/b",
+		"[email protected]:a/b.git": "[email protected]:a/b.git",
+		"":                       "",
+		"-":                      "",
+		"  spaced/x  ":           "https://github.com/spaced/x",
+	}
+	for in, want := range cases {
+		if got := railwayRepoURL(in); got != want {
+			t.Errorf("railwayRepoURL(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+func TestEdgesOf(t *testing.T) {
+	obj := map[string]interface{}{
+		"services": map[string]interface{}{
+			"edges": []interface{}{
+				map[string]interface{}{"node": map[string]interface{}{"id": "a", "name": "web"}},
+				map[string]interface{}{"node": map[string]interface{}{"id": "b", "name": "api"}},
+			},
+		},
+	}
+	nodes := edgesOf(obj, "services")
+	if len(nodes) != 2 || str(nodes[0], "name") != "web" {
+		t.Fatalf("edgesOf returned %+v", nodes)
+	}
+	if got := edgesOf(obj, "missing"); len(got) != 0 {
+		t.Fatalf("edgesOf(missing) = %+v, want empty", got)
+	}
+	if got := edgesOf(map[string]interface{}{"services": nil}, "services"); len(got) != 0 {
+		t.Fatalf("edgesOf(nil conn) = %+v, want empty", got)
+	}
+}