Fix backup restore dropping library entries (#3667)

* Fix backup restore dropping library entries

History restore resolved chapters by URL alone, so a backup holding the
same entry twice under one source matched multiple chapter rows and threw
`ResultSet returned more than 1 row`. Scope the lookups to the entry.

Entries are restored in chunks of 100 sharing one transaction. SQLDelight
fails the enclosing transaction when a nested one fails, so catching the
per-entry exception did not contain it and the whole chunk rolled back,
losing up to 100 entries per bad one. Retry entry by entry on failure.

Refs #647

* Update changelog

---------

Co-authored-by: Naji Astier <na-ji@users.noreply.github.com>

CHANGELOG.md

@@ -33,6 +33,7 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
 - Fixed app bars remaining visible after changing pages by tapping in the paged reader after using the chapter navigator slider ([@AntsyLich](https://github.com/AntsyLich)) ([#3567](https://github.com/mihonapp/mihon/pull/3567))
 - Fixed MangaBaka User Agent string ([@MajorTanya](https://github.com/MajorTanya)) ([#3578](https://github.com/mihonapp/mihon/pull/3578))
 - Fixed extension installation with shizuku installer ([@NGB-Was-Taken](https://github.com/NGB-Was-Taken)) ([#3630](https://github.com/mihonapp/mihon/pull/3630))
+- Fixed backup restore dropping library entries when the backup contains duplicate chapters ([@na-ji](https://github.com/na-ji)) ([#3667](https://github.com/mihonapp/mihon/pull/3667))
 
 ## [v0.20.1] - 2026-07-09
 ### Added