feat: attachments on tickets and comments

Files are uploaded over REST, stored on disk (a volume in Docker) and
recorded on the ticket as events; the bytes are written first, so no
attachment ever points at a missing file. Only images, video, audio, PDF
and plain text are shown inline, everything with nosniff and a sandbox CSP.
The web shows thumbnails, uploads by drag and drop or by pasting a
screenshot, and attaches files to new comments.

Also adds `nx run api:contracts`, which writes schema.gql and
openapi.json without starting the API or any database.

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

libs/api/tracker/application/src/lib/event-handlers/event-handlers.ts

@@ -24,6 +24,9 @@ import { ProjectSettingsChangedEventHandler } from './project-settings-changed.e
 import { ProjectDeletedEventHandler } from './project-deleted.event-handler';
 import { IssueDeletedEventHandler } from './issue-deleted.event-handler';
 import { ReleaseDeletedEventHandler } from './release-deleted.event-handler';
+import { IssueAttachmentAddedEventHandler } from './issue-attachment-added.event-handler';
+import { IssueAttachmentRemovedEventHandler } from './issue-attachment-removed.event-handler';
+import { AttachmentCleanupEventHandler } from './attachment-cleanup.event-handler';
 
 /** Read-model projections (MongoDB) + realtime, fed by the EventsBridge. */
 export const EVENT_HANDLERS = [
@@ -52,6 +55,9 @@ export const EVENT_HANDLERS = [
   ReleaseCreatedEventHandler,
   ReleaseShippedEventHandler,
   ReleaseUpdatedEventHandler,
+  IssueAttachmentAddedEventHandler,
+  IssueAttachmentRemovedEventHandler,
+  AttachmentCleanupEventHandler,
 ];
 
 export { ReadModelNotifier };