refactor: simplify architecture and harden lifecycle

Remove obsolete implementations, centralize background task ownership and terminal-state recovery, consolidate frontend routing and log streaming, and enforce project-wide verification in CI.

server/internal/service/node_service_test.go

@@ -20,6 +20,7 @@ func openNodeServiceDB(t *testing.T) *gorm.DB {
 	if err != nil {
 		t.Fatalf("open: %v", err)
 	}
+	closeTestDatabase(t, db)
 	if err := db.AutoMigrate(&model.Node{}); err != nil {
 		t.Fatalf("migrate: %v", err)
 	}