feat(scenarios): overhaul export/import with multi-entity YAML format

- export now accepts includeEnvironment and credentialIds query params
- output is a YAML stream with comment-delimited environment, credential, and scenario sections
- scenario entity includes credentials array with alias mappings
- import accepts both old single-object and new array format, upserts envs/creds before linking
- new ExportScenarioModal with env and per-credential checkboxes replaces direct download

server/src/mcp/mcp.service.ts

@@ -965,7 +965,10 @@ export class McpService {
       },
       async ({ id }) => {
         try {
-          const exported = await this.scenarioService.exportScenario(id);
+          const exported = await this.scenarioService.exportScenario(id, {
+            includeEnvironment: false,
+            credentialIds: [],
+          });
           return {
             content: [
               { type: "text" as const, text: JSON.stringify(exported) },
@@ -1010,11 +1013,10 @@ export class McpService {
       async ({ name, description, steps }) => {
         try {
           const scenario = await this.scenarioService.importScenario({
+            kind: "scenario",
             name,
             description,
-            steps: steps as Parameters<
-              typeof this.scenarioService.importScenario
-            >[0]["steps"],
+            steps: steps as { title: string | null; execCode: string | null }[],
           });
           return {
             content: [