bugfix: gate manga PATCH and cover endpoints on uploader (0.34.1)

PATCH /mangas/:id, PUT /mangas/:id/cover and DELETE /mangas/:id/cover
took the current user but never compared it against the row's
uploaded_by. Any signed-in user could overwrite or clear any manga's
metadata and cover. Add require_can_edit gate: non-NULL uploaded_by
must match the caller; legacy NULL rows stay open until an admin role
lands (per migration 0011 historical-data note).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.34.0"
+version = "0.34.1"
 edition = "2021"
 default-run = "mangalord"