feat: import and export tickets as CSV

Every ticket of a project can be downloaded as CSV, and a CSV exported
from TaskStream or from Jira can be imported: types, statuses, priorities
and people are matched by id or name, the rest falls back with a warning,
and parents are rebuilt. The settings page previews an import before it
creates anything.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/web/tracker/domain/src/lib/ports/gateways.ts

@@ -6,6 +6,7 @@ import {
   Comment,
   Epic,
   GitIntegration,
+  ImportReport,
   Webhook,
   WebhookDelivery,
   SavedFilter,
@@ -133,6 +134,17 @@ export abstract class IssuesGateway {
   ): Observable<CommandResult>;
 }
 
+/** Tickets in and out as CSV. */
+export abstract class TransferGateway {
+  abstract exportCsv(projectId: string): Observable<Blob>;
+  /** `dryRun`: only tell what would be created. */
+  abstract importCsv(
+    projectId: string,
+    file: File,
+    dryRun: boolean,
+  ): Observable<ImportReport>;
+}
+
 /** The project's outgoing webhooks (owners and admins). */
 export abstract class WebhooksGateway {
   abstract list(projectId: string): Observable<Webhook[]>;