fix(sync): short sync transactions, real Steam retries, no N+1

readme.md

@@ -14,7 +14,11 @@ To Be Played is split into three repositories:
 ## Features
 
 - **Steam sync**: owned games, playtime and achievements through the Steam Web API. Manual sync plus a nightly
-  sync. Resilience4j retries and rate-limits every Steam call; Caffeine caches game counts and player summaries.
+  sync. Resilience4j rate-limits every Steam call and tries the owned games up to three times (never again on a 4xx;
+  the wishlist and the calls a page waits for once); Caffeine caches game counts and player summaries. A sync commits its claim (`RUNNING`, with
+  `sync_started_at`), its writes and its finish apart, and calls Steam and IGDB outside any transaction: a second
+  sync sees `RUNNING` and skips, a failed one stores `FAILED`. A run older than `app.library.running-stale-minutes`
+  can be taken over; its own finish then changes nothing.
 - **Backlog**: status (`BACKLOG`, `PLAYING`, `FINISHED`, `COMPLETED` = 100 %, `DROPPED`), rating 1–5, notes, priority,
   filters and sorting. "Pile of Shame" summary with a random suggestion of what to play.
 - **Picker**: up to 10 random backlog games for a time budget (IGDB normal time to beat) and a mood, HIGH priority