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/infrastructure/src/lib/adapters/http-transfer.gateway.ts

@@ -0,0 +1,58 @@
+import { HttpClient, HttpHeaders } from '@angular/common/http';
+import { inject, Injectable } from '@angular/core';
+import {
+  AccessTokenSource,
+  API_CONFIG,
+} from '@task-stream/web/shared/infrastructure';
+import { ImportReport, TransferGateway } from '@task-stream/web/tracker/domain';
+import { from, Observable, switchMap } from 'rxjs';
+
+/** CSV files travel over REST, like attachments. */
+@Injectable()
+export class HttpTransferGateway extends TransferGateway {
+  private readonly http = inject(HttpClient);
+  private readonly api = inject(API_CONFIG);
+  private readonly tokens = inject(AccessTokenSource);
+
+  exportCsv(projectId: string): Observable<Blob> {
+    return this.authorized((headers) =>
+      this.http.get(`${this.base(projectId)}/export.csv`, {
+        headers,
+        responseType: 'blob',
+      }),
+    );
+  }
+
+  importCsv(
+    projectId: string,
+    file: File,
+    dryRun: boolean,
+  ): Observable<ImportReport> {
+    const body = new FormData();
+    body.append('file', file, file.name);
+    return this.authorized((headers) =>
+      this.http.post<ImportReport>(`${this.base(projectId)}/import`, body, {
+        headers,
+        params: { dryRun: String(dryRun) },
+      }),
+    );
+  }
+
+  private base(projectId: string): string {
+    return `${this.api.restUrl}/projects/${encodeURIComponent(projectId)}`;
+  }
+
+  private authorized<T>(
+    request: (headers: HttpHeaders) => Observable<T>,
+  ): Observable<T> {
+    return from(this.tokens.accessToken()).pipe(
+      switchMap((token) =>
+        request(
+          token
+            ? new HttpHeaders({ Authorization: `Bearer ${token}` })
+            : new HttpHeaders(),
+        ),
+      ),
+    );
+  }
+}