feat: add snapshot/rollback system with download capability

- Add AppSnapshot entity with type (pre_deploy/manual), status tracking, and file paths
- Add SnapshotsService with create, capture, rollback, prune (max 10), and download logic
- Add SnapshotsController with REST endpoints for CRUD, rollback, and file downloads
- Add K8s methods: exportDatabaseDump, archiveWpContent, restoreWpContent
- Auto-create pre-deploy snapshots before each deployment for rollback safety
- Support downloading current live state (source, wp-content, database) without snapshots
- Add snapshot management UI in app detail page with create, rollback, download, delete
- Wire circular dependencies with forwardRef between Deployments and Snapshots modules

frontend/src/types/index.ts

@@ -287,3 +287,27 @@ export interface CostBreakdown {
   yearly: number;
   breakdown: { label: string; hourly: number; monthly: number; yearly: number }[];
 }
+
+// ─── Snapshot / Rollback types ──────────────────────
+
+export type SnapshotType = 'pre_deploy' | 'manual';
+export type SnapshotStatus = 'in_progress' | 'completed' | 'failed';
+
+export interface AppSnapshot {
+  id: string;
+  type: SnapshotType;
+  status: SnapshotStatus;
+  label?: string;
+  appArchivePath?: string;
+  wpContentArchivePath?: string;
+  imageTag?: string;
+  dbDumpPath?: string;
+  hasDatabase: boolean;
+  appArchiveSize?: number;
+  dbDumpSize?: number;
+  wpContentSize?: number;
+  errorMessage?: string;
+  applicationId: string;
+  createdBy: string;
+  createdAt: string;
+}