feat: add saveSession flag to create scenario runs

- Add optional `saveSession` boolean parameter to CreateScenarioRunDto
- Add `saveSession` column to ScenarioRunEntity
- When saveSession=true and run completes, preserve the browser context as a named explore session instead of closing it
- Session name follows pattern: run-{runId}
- Automatically extracts token and localStorage for session persistence
- Injected SessionService and SessionContextService into ScenarioSchedulerService
- Updated MCP run_scenario tool to accept saveSession parameter
- Updated UI run dialog with checkbox to enable session preservation
- Client API updated to pass saveSession flag

server/src/scenario/dto/create-scenario-run.dto.ts

@@ -1,7 +1,11 @@
-import { IsNotEmpty, IsUUID } from "class-validator";
+import { IsBoolean, IsNotEmpty, IsOptional, IsUUID } from "class-validator";
 
 export class CreateScenarioRunDto {
   @IsUUID()
   @IsNotEmpty()
   environmentId: string;
+
+  @IsBoolean()
+  @IsOptional()
+  saveSession?: boolean;
 }