update changelogs

Author: kafkas

fern/products/sdks/overview/swift/changelog/2025-09-09.mdx

@@ -1,3 +1,7 @@
+## 0.12.4
+**`(fix):`** Fixed incorrect handling of schema `date` fields — now decoded into a new `CalendarDate` type.
+
+
 ## 0.12.3
 **`(fix):`** Added missing system dependencies (bash, curl, git, zip) to Swift generator Docker image to fix README generation.