feat(files): add file storage subsystem with scenario and run artifact support

- add FileEntity, ScenarioFileEntity, ScenarioRunFileEntity with UUID-sharded disk tree
- FileStorageService: write/sha256/expiry, paginated listing, dynamic cleanup cron via SchedulerRegistry
- expose getScenarioFiles() and downloadFile() on ScriptContext for use in exec code
- wire scenarioId, runId, fileService into ExecContextBuilder and scenario scheduler
- add file upload and listing endpoints to ScenarioController
- add FILES_DIR, FILE_RUN_EXPIRATION_DAYS, FILE_CLEANUP_CRON to AppConfig

server/src/file/scenario-run-file.entity.ts

@@ -0,0 +1,33 @@
+import {
+  Column,
+  CreateDateColumn,
+  Entity,
+  JoinColumn,
+  ManyToOne,
+  PrimaryGeneratedColumn,
+} from "typeorm";
+import { ScenarioRunEntity } from "../scenario/scenario-run.entity";
+import { FileEntity } from "./file.entity";
+
+@Entity("scenario_run_files")
+export class ScenarioRunFileEntity {
+  @PrimaryGeneratedColumn("uuid")
+  id: string;
+
+  @Column()
+  runId: string;
+
+  @Column()
+  fileId: string;
+
+  @ManyToOne(() => ScenarioRunEntity, { onDelete: "CASCADE" })
+  @JoinColumn({ name: "runId" })
+  run: ScenarioRunEntity;
+
+  @ManyToOne(() => FileEntity, { onDelete: "CASCADE" })
+  @JoinColumn({ name: "fileId" })
+  file: FileEntity;
+
+  @CreateDateColumn()
+  createdAt: Date;
+}