feat(scenarios): link scenarios to a default environment

- add optional ManyToOne relation from scenario to environment entity
- expose environmentId in create/update DTOs, service, and MCP tools
- pre-select linked environment in run modals on detail and list pages
- add environment selector to create/edit scenario forms
- show linked environment as a navigable link on scenario detail page

server/src/mcp/mcp.service.ts

@@ -472,13 +472,18 @@ export class McpService {
             .string()
             .optional()
             .describe("Optional markdown description"),
+          environmentId: z
+            .uuid()
+            .optional()
+            .describe("Optional linked environment ID"),
         },
       },
-      async ({ name, description }) => {
+      async ({ name, description, environmentId }) => {
         try {
           const scenario = await this.scenarioService.create({
             name,
             description,
+            environmentId,
           });
           return {
             content: [
@@ -505,13 +510,19 @@ export class McpService {
             .string()
             .optional()
             .describe("New markdown description"),
+          environmentId: z
+            .uuid()
+            .nullable()
+            .optional()
+            .describe("Linked environment ID (null to unlink)"),
         },
       },
-      async ({ id, name, description }) => {
+      async ({ id, name, description, environmentId }) => {
         try {
           const scenario = await this.scenarioService.update(id, {
             name,
             description,
+            environmentId,
           });
           return {
             content: [