PostgreSQL: Add variable query editor support

- Introduced a new feature toggle for the PostgreSQL variable query editor `postgresVariableQueryEditor`.

pkg/services/featuremgmt/registry.go

@@ -1913,6 +1913,13 @@ var (
 			Stage:       FeatureStageExperimental,
 			Owner:       grafanaOSSBigTent,
 		},
+		{
+			Name:         "postgresVariableQueryEditor",
+			Description:  "Enable the new variable query editor for the PostgreSQL data source",
+			Stage:        FeatureStageExperimental,
+			Owner:        grafanaOSSBigTent,
+			FrontendOnly: true,
+		},
 		{
 			Name:         "pluginStoreServiceLoading",
 			Description:  "Load plugins on store service startup instead of wire provider, and call RegisterFixedRoles after all plugins are loaded",

pkg/services/featuremgmt/toggles_gen.csv

@@ -260,6 +260,7 @@ newVizSuggestions,preview,@grafana/dataviz-squad,false,false,true
 externalVizSuggestions,experimental,@grafana/dataviz-squad,false,false,true
 preventPanelChromeOverflow,preview,@grafana/grafana-frontend-platform,false,false,true
 jaegerEnableGrpcEndpoint,experimental,@grafana/oss-big-tent,false,false,false
+postgresVariableQueryEditor,experimental,@grafana/oss-big-tent,false,false,true
 pluginStoreServiceLoading,experimental,@grafana/plugins-platform-backend,false,false,false
 newPanelPadding,preview,@grafana/dashboards-squad,false,false,true
 onlyStoreActionSets,GA,@grafana/identity-access-team,false,false,false

pkg/services/featuremgmt/toggles_gen.json

@@ -2692,6 +2692,19 @@
         "expression": "false"
       }
     },
+    {
+      "metadata": {
+        "name": "postgresVariableQueryEditor",
+        "resourceVersion": "1765231394616",
+        "creationTimestamp": "2025-12-08T22:03:14Z"
+      },
+      "spec": {
+        "description": "Enable the new variable query editor for the PostgreSQL data source",
+        "stage": "experimental",
+        "codeowner": "@grafana/oss-big-tent",
+        "frontend": true
+      }
+    },
     {
       "metadata": {
         "name": "preferLibraryPanelTitle",