feat: grid skeletons on the author and collection detail pages

Both loaders now stream their manga grid instead of blocking on it: the cheap
header renders immediately (and still handles 404/401 in the loader) while a
MangaGridSkeleton stands in until the grid resolves, then swaps in without a
layout shift. Collection detail seeds its optimistic-removal state from the
stream via a guarded effect.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.117.0",
+  "version": "0.118.0",
   "private": true,
   "type": "module",
   "scripts": {