Fix watchlist add and thumbnail API validation

README.md

@@ -2,7 +2,7 @@
 
 A local web UI for a system-wide `ani-cli` install.
 
-Current version: `0.29.2`
+Current version: `0.29.3`
 
 ## Project Layout
 
@@ -62,6 +62,7 @@ The app currently includes:
 - A dedicated Config page for saved default folder, mode, and quality settings.
 - A paged SQLite-backed download queue with retry, cancel, remove, retry-failed, and clear-finished actions.
 - A paged SQLite-backed watchlist with summary cards, per-show refresh, bulk refresh, source links, and thumbnail tools.
+- Duplicate watchlist adds now return `200 OK` with `created: false`, keeping the API status aligned with the no-op result.
 - Watchlist category tabs for `Watching`, `Planned`, `Finished`, and `Dropped`, with per-anime category editing.
 - AnimeSchedule-backed watchlist completion tracking that compares live sub/dub availability with the expected total episode count when known.
 - Automatic watchlist sync after successful downloads, including downloaded-vs-manual finished markers.
@@ -215,6 +216,7 @@ Current thumbnail behavior:
 - Cached thumbnails render from the local project cache when available.
 - The page adds a fresh nonce to thumbnail URLs to avoid stale browser-cached misses.
 - Missing visible covers are warmed up in small batches instead of one request per card all at once.
+- The thumbnail warm-up API now requires `show_ids` to be a JSON array and accepts explicit boolean-style `force` values such as `true` and `false`.
 - The page only retries an unresolved cover warm-up once per thumbnail state change during the current browser session, so silent watchlist polling does not keep hammering the same missing poster.
 - If a show disappears while a thumbnail warm-up batch is running, that entry is skipped cleanly instead of failing the whole batch request.
 - Thumbnail image tags only hit the local route for already-cached files, so opening the watchlist no longer triggers a per-card remote lookup burst.