fix(delete): prune in-memory SerieList cache after delete

delete_series() removed the row from the database and the folder
from disk, but never evicted the entry from SerieList.keyDict — the
in-memory cache that list_series_with_filters() reads from via
SeriesApp.list.GetList(). As a result /api/anime kept returning the
deleted series on every page reload (the 'Beyblade Burst still listed
after delete' bug).

Changes:
* Add SerieList.remove(key) so the cache has a proper eviction API.
* In delete_series(), call it (or fall back to keyDict.pop) after a
  successful DB delete.
* Broadcast a broader series_list_changed event so any client that
  missed the specific series_deleted event can re-sync by re-fetching
  /api/anime. Front-end: new SERIES_LIST_CHANGED constant, handler
  that triggers SeriesManager.reloadSeries().
* Two new regression tests: one asserting the in-memory cache is
  pruned, one asserting the broader broadcast fires.

src/server/web/static/js/index/series-manager.js

@@ -584,6 +584,17 @@ AniWorld.SeriesManager = (function() {
         }
     }
 
+    /**
+     * Re-fetch the series list from the server. Used as a durable
+     * backstop when receiving the broader series_list_changed WS event
+     * so local state cannot drift from the server's in-memory cache.
+     * @returns {Promise<void>}
+     */
+    function reloadSeries() {
+        console.info('[SeriesManager] Reloading series from server');
+        return loadSeries();
+    }
+
     // Public API
     return {
         init: init,
@@ -596,6 +607,7 @@ AniWorld.SeriesManager = (function() {
         updateSeriesLoadingStatus: updateSeriesLoadingStatus,
         updateSingleSeries: updateSingleSeries,
         updateSeriesKey: updateSeriesKey,
-        removeSeries: removeSeries
+        removeSeries: removeSeries,
+        reloadSeries: reloadSeries
     };
 })();

src/server/web/static/js/index/socket-handler.js

@@ -169,6 +169,17 @@ AniWorld.IndexSocketHandler = (function() {
             }
         });
 
+        // Series list membership changed (delete, bulk import, rescan, …).
+        // Re-fetch /api/anime so local state cannot drift from the server's
+        // in-memory cache. Acts as a durable backstop when the more specific
+        // series_deleted event does not reach the client.
+        socket.on(WS_EVENTS.SERIES_LIST_CHANGED, function(data) {
+            console.info('[SocketHandler] Series list changed:', data);
+            if (AniWorld.SeriesManager && AniWorld.SeriesManager.reloadSeries) {
+                AniWorld.SeriesManager.reloadSeries();
+            }
+        });
+
         // Download events
         socket.on(WS_EVENTS.DOWNLOAD_STARTED, function(data) {
             isDownloading = true;

src/server/web/static/js/shared/constants.js

@@ -105,6 +105,10 @@ AniWorld.Constants = (function() {
         SERIES_UPDATED: 'series_updated',
         SERIES_LOADING_UPDATE: 'series_loading_update',
         SERIES_DELETED: 'series_deleted',
+        // Fires when the membership of the series list changes (delete,
+        // bulk import, rescan completion, …). Clients should re-fetch
+        // /api/anime to resync with the server's in-memory cache.
+        SERIES_LIST_CHANGED: 'series_list_changed',
 
         // Scheduled scan events
         SCHEDULED_RESCAN_STARTED: 'scheduled_rescan_started',