feat(browser,mcp): resolve environment and credentials from DB in exec

- POST /exec now accepts environmentId (UUID) and credentials (alias → UUID)
  instead of raw payloads; resolves entities via EnvironmentService and
  CredentialService before passing data to browserService.exec
- exec_code MCP tool updated with same schema: environmentId + credentials map
- CredentialModule imported into BrowserModule and McpModule
- docs(scenario): rewrite script runtime section for single context argument
- docs(mcp): update exec_code description to reflect new parameter shapes
- style: reorder imports across server source (formatter)

server/src/session/session.module.ts

@@ -1,10 +1,10 @@
 import { Module } from "@nestjs/common";
 import { TypeOrmModule } from "@nestjs/typeorm";
-import { SessionEntity } from "./session.entity";
-import { SessionService } from "./session.service";
-import { SessionController } from "./session.controller";
 import { SessionContextService } from "./session-context.service";
 import { SessionSchedulerService } from "./session-scheduler.service";
+import { SessionController } from "./session.controller";
+import { SessionEntity } from "./session.entity";
+import { SessionService } from "./session.service";
 
 @Module({
   imports: [TypeOrmModule.forFeature([SessionEntity])],