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/models/models.ts

@@ -191,6 +191,17 @@ export interface Webhook {
   lastDelivery: WebhookDelivery | null;
 }
 
+/** What an import did (or, as a preview, would do). */
+export interface ImportReport {
+  format: 'taskstream' | 'jira';
+  dryRun: boolean;
+  rows: number;
+  created: number;
+  keys: string[];
+  skipped: { line: number; reason?: string }[];
+  warnings: { line: number; message?: string }[];
+}
+
 /** The project's webhook for GitHub, Gitea or GitLab. */
 export interface GitIntegration {
   enabled: boolean;