fix: upload retry reuses the created manga instead of duplicating it

After a partial upload failure (manga created, a chapter failed), re-submitting
re-ran createManga and spawned a duplicate manga. Track the created manga id:
a retry skips creation, re-sends only the not-yet-done chapters, disables the
now-saved title, relabels the button "Retry failed chapters", and shows a note.

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

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.128.0",
+  "version": "0.128.1",
   "private": true,
   "type": "module",
   "scripts": {