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/web/tracker/application/src/lib/facades/issue.facade.ts

@@ -1,10 +1,13 @@
 import { inject, Injectable, Provider } from '@angular/core';
 import { injectDispatch } from '@ngrx/signals/events';
 import {
+  Attachment,
+  AttachmentsGateway,
   IssueLink,
   IssueLinkType,
   UpdateIssueInput,
 } from '@task-stream/web/tracker/domain';
+import { Observable } from 'rxjs';
 import { issuePageEvents } from '../events/issue.events';
 import { IssueStore } from '../stores/issue.store';
 
@@ -16,6 +19,7 @@ import { IssueStore } from '../stores/issue.store';
 export class IssueFacade {
   private readonly store = inject(IssueStore);
   private readonly dispatch = injectDispatch(issuePageEvents);
+  private readonly files = inject(AttachmentsGateway);
 
   readonly issue = this.store.issue;
   readonly comments = this.store.comments;
@@ -74,12 +78,33 @@ export class IssueFacade {
     );
   }
 
-  addComment(body: string): void {
+  /** `files` are attached under the new comment. */
+  addComment(body: string, files: File[] = []): void {
     this.withIssue((issueId) =>
-      this.dispatch.commentAddRequested({ issueId, body }),
+      this.dispatch.commentAddRequested({ issueId, body, files }),
     );
   }
 
+  /** Attaches files to the ticket (or under one of its comments). */
+  attach(files: File[], commentId: string | null = null): void {
+    if (!files.length) return;
+    this.withIssue((issueId) =>
+      this.dispatch.attachRequested({ issueId, files, commentId }),
+    );
+  }
+
+  removeAttachment(attachmentId: string): void {
+    this.withIssue((issueId) =>
+      this.dispatch.attachmentRemoveRequested({ issueId, attachmentId }),
+    );
+  }
+
+  /** The file's bytes, to show an image or save the file. */
+  fileOf(attachment: Attachment): Observable<Blob> {
+    const issueId = this.store.issue()?.id ?? '';
+    return this.files.download(issueId, attachment);
+  }
+
   editComment(commentId: string, body: string): void {
     this.dispatch.commentEditRequested({ commentId, body });
   }