chore(release): v0.13.1

Pages answer from the cache again: database reads no longer wait behind
writes, the listing query uses its indexes, and a cache answer races the
server instead of waiting it out. Plus the series page's single season
walk and the background-audio return fix.

CHANGELOG.md

@@ -9,6 +9,36 @@ generated trace matrix lives in [docs/traceability.md](docs/traceability.md).
 For how long each fixed defect had been shipping before it was found, see
 [docs/defect-windows.md](docs/defect-windows.md).
 
+## v0.13.1
+
+Pages answer from the cache again. Found on a Fairphone, where opening a
+series took one to ten seconds even though everything on it was already cached.
+
+### ⚡ Performance
+
+- **Series and library pages load from the cache.** Frasier's season and
+  episode lists now appear in 34–133 ms on a Fairphone 5; they took 600–1030 ms
+  each, waiting on the server. Three causes stacked up. Every database read
+  waited behind every write, because one connection served the whole app. The
+  listing query scanned the entire cached catalogue whatever page it was for.
+  And a cache answer that took longer than 100 ms was ignored until the server
+  replied. Reads now have their own connections, the query uses its indexes
+  (about 50× faster on a 100k-item cache), and the cache and the server race:
+  whichever answers first with something to show wins. (DR-012, DR-013)
+- **A series page walks its seasons once, in parallel.** It used to walk all of
+  them twice, one after another. (DR-295)
+
+### 🐛 Fixes
+
+- **Coming back from background audio opens the right episode.** If an episode
+  ended while the app was in the background, returning to it reloaded the
+  *previous* episode at the new one's position. (DR-296)
+- **Offline changes keep their own identity.** Two favourites or progress
+  updates queued at the same moment could be handed each other's queue entry,
+  so syncing one marked the other as done. (DR-014)
+- **Catalog caching no longer switches off data-integrity checks for the rest
+  of the app** while it saves a page. (DR-012)
+
 ## v0.13.0
 
 Android plays and downloads the original file, and offline mode works without