Added RNs for v2025.21.0

Author: Pantofel102

docs/Coiote_IoT_DM/Release_Notes/v2025.21.0.md

@@ -0,0 +1,21 @@
+# v2025.21.0
+
+Previous version: [v2025.20.0](./v2025.20.0.md)
+
+## Enhancements
+
+**Clearer error messages for FOTA failures**    
+
+FOTA error reporting now shows clear messages when updates fail due to the device not being reachable or a message timeout. This makes it easier to understand the reason behind a failed update.
+
+**Documentation for group-level widgets**   
+
+Added user documentation for the feature that allows creating widgets directly at the group level. This improves usability by ensuring users can find guidance on managing visualizations for grouped devices.
+
+**Error message for mass device removal**   
+
+Added a snackbar message when mass device removal fails due to outdated or changed filter settings. This ensures users are now clearly informed about removal errors.
+
+**Improved FOTA file upload**   
+
+Rewritten the FOTA file upload mechanism to use multi-part uploads, enabling better handling of large files. This improves reliability when uploading firmware images and aligns it with the SOTA file upload flow.

mkdocs.yml

@@ -117,6 +117,7 @@ nav:
                     - API reference: 'Coiote_IoT_DM/API_documentation/api_reference.md'
             - 'Release Notes':
                         - 2025:
+                            - 'Coiote_IoT_DM/Release_Notes/v2025.21.0.md'
                             - 'Coiote_IoT_DM/Release_Notes/v2025.20.0.md'
                             - 'Coiote_IoT_DM/Release_Notes/v2025.18.0.md'
                             - 'Coiote_IoT_DM/Release_Notes/v2025.17.0.md'