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>

apps/api/scripts/register.cjs

@@ -0,0 +1,21 @@
+/*
+ * Lets Node run the TypeScript sources of the monorepo directly: compiles
+ * them on the fly (decorator metadata included, which Nest needs) and
+ * resolves the `@task-stream/*` aliases of tsconfig.base.json.
+ */
+const { join } = require('node:path');
+const root = join(__dirname, '../../..');
+
+require('ts-node').register({
+  project: join(root, 'apps/api/tsconfig.app.json'),
+  transpileOnly: true,
+  compilerOptions: {
+    module: 'commonjs',
+    moduleResolution: 'node10',
+    ignoreDeprecations: '6.0',
+  },
+});
+require('tsconfig-paths').register({
+  baseUrl: root,
+  paths: require(join(root, 'tsconfig.base.json')).compilerOptions.paths,
+});