fix: add batch delay

.env.example

@@ -138,6 +138,11 @@ BATCH_DELAY=5.0
 # Maximum concurrent series processing
 MAX_CONCURRENT_SERIES=3
 
+# Sequential processing delay for bulk downloads (seconds)
+# When multiple episodes are downloaded at once, process them one by one with this delay
+# Set to 0 to disable sequential processing (parallel mode)
+SEQUENTIAL_DELAY=20.0
+
 # API timeout in seconds
 TIMEOUT_SECONDS=45