Fix image deletion: per-tag delete, repository delete, daily GC.

- Deleting a tag now untags only that tag; the manifest is removed only when
  no other tag references the same digest (previously deleting by digest also
  removed every sibling tag).
- Add repository deletion. The registry API cannot drop a repository from the
  catalog, so empty repositories stayed in the UI forever with nothing left to
  delete. The app now mounts registry storage and removes the repository's
  metadata directories after deleting its manifests.
- Run `registry garbage-collect` daily (GC_HOUR_UTC) so deleted blobs free disk.
- Disable Watchtower for the locally built app image.

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

app/server/utils/registry.ts

@@ -95,3 +95,39 @@ export async function deleteManifest(name: string, digest: string): Promise<void
     })
   }
 }
+
+/**
+ * Remove a single tag. Other tags pointing at the same manifest are kept; the
+ * manifest itself is deleted only when no tag references it anymore, so blobs
+ * become reclaimable by `registry garbage-collect`.
+ */
+export async function deleteTag(
+  name: string,
+  tag: string,
+): Promise<{ digest: string; manifestDeleted: boolean }> {
+  const digest = await getManifestDigest(name, tag)
+  if (!digest) {
+    throw createError({ statusCode: 404, statusMessage: 'Tag not found' })
+  }
+
+  const res = await registryFetch(
+    `/v2/${encodeURI(name)}/manifests/${encodeURIComponent(tag)}`,
+    { method: 'DELETE' },
+    [{ type: 'repository', name, actions: ['delete', 'pull'] }],
+  )
+  if (!res.ok && res.status !== 404) {
+    throw createError({
+      statusCode: 502,
+      statusMessage: `Registry tag delete failed: ${res.status}`,
+    })
+  }
+
+  const remaining = await listTags(name)
+  const remainingDigests = await Promise.all(remaining.map((t) => getManifestDigest(name, t)))
+  if (remainingDigests.includes(digest)) {
+    return { digest, manifestDeleted: false }
+  }
+
+  await deleteManifest(name, digest)
+  return { digest, manifestDeleted: true }
+}