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/infrastructure/src/lib/tracker-infrastructure.providers.ts

@@ -4,6 +4,7 @@ import {
 } from '@angular/core';
 import {
   ActivityGateway,
+  AttachmentsGateway,
   CommentsGateway,
   IssuesGateway,
   ProjectsGateway,
@@ -18,10 +19,11 @@ import {
   GraphqlUsersGateway,
 } from './adapters/graphql-collaboration.gateways';
 import { GraphqlIssuesGateway } from './adapters/graphql-issues.gateway';
+import { HttpAttachmentsGateway } from './adapters/http-attachments.gateway';
 import { GraphqlProjectsGateway } from './adapters/graphql-projects.gateway';
 import { GraphqlRealtimeGateway } from './adapters/graphql-realtime.gateway';
 
-/** Ports → GraphQL adapters. */
+/** Ports → GraphQL adapters (and REST for files). */
 export function provideTrackerInfrastructure(): EnvironmentProviders {
   return makeEnvironmentProviders([
     { provide: ProjectsGateway, useClass: GraphqlProjectsGateway },
@@ -29,6 +31,7 @@ export function provideTrackerInfrastructure(): EnvironmentProviders {
     { provide: CommentsGateway, useClass: GraphqlCommentsGateway },
     { provide: ReleasesGateway, useClass: GraphqlReleasesGateway },
     { provide: ActivityGateway, useClass: GraphqlActivityGateway },
+    { provide: AttachmentsGateway, useClass: HttpAttachmentsGateway },
     { provide: UsersGateway, useClass: GraphqlUsersGateway },
     { provide: TrackerRealtimeGateway, useClass: GraphqlRealtimeGateway },
   ]);