Update changelogs from fern repo (#4428)

Author: fern-support

fern/products/sdks/overview/csharp/changelog/2026-03-20.mdx

@@ -1,3 +1,14 @@
+## 2.48.0
+**`(feat):`** Add bounded send queue with message expiration to `WebSocketConnection`. The
+unbounded `Channel<T>` queues are replaced with configurable bounded channels
+(`SendQueueLimit`, default: 10,000) that use `BoundedChannelFullMode.DropWrite`
+to reject new messages when the queue is full. A `SendCacheItemTimeout` property
+(default: 30 minutes) causes stale messages to be silently dropped during drain,
+preventing memory growth during network outages and avoiding sending outdated
+messages after reconnection. Set `SendQueueLimit` to 0 for unbounded or
+`SendCacheItemTimeout` to null to disable expiration.
+
+
 ## 2.47.0
 **`(feat):`** Add receive hang detection via a background state monitor task. A new
 `StateCheckInterval` property (default: 5 seconds) controls how often the