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/snippet/snippet.service.ts

@@ -6,14 +6,14 @@ import {
 } from "@nestjs/common";
 import { InjectRepository } from "@nestjs/typeorm";
 import { Repository } from "typeorm";
-import { SnippetEntity } from "./snippet.entity";
-import { CreateSnippetDto } from "./dto/create-snippet.dto";
-import { UpdateSnippetDto } from "./dto/update-snippet.dto";
-import { SnippetExportDto } from "./dto/snippet-export.dto";
 import {
-  PaginationQueryDto,
   PaginatedResult,
+  PaginationQueryDto,
 } from "../common/dto/pagination.dto";
+import { CreateSnippetDto } from "./dto/create-snippet.dto";
+import { SnippetExportDto } from "./dto/snippet-export.dto";
+import { UpdateSnippetDto } from "./dto/update-snippet.dto";
+import { SnippetEntity } from "./snippet.entity";
 
 export type SnippetOrderBy = "id" | "alias" | "title" | "createdAt" | "updatedAt";