Update changelog

CHANGELOG.md

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 ## Changelog
 
-#### 2.631 (April, 2026)
+#### 2.640 (May 4, 2026)
+* Add new nftables module with profiles, saved tables, and chains/sets management
+* Add new Nginx module with look and feel matching the Apache module
+* Add option to hide sensitive values (like passwords or tokens) from Webmin's request logs
+* Add custom ACME server support for Webmin SSL renewal
+* Add support for the latest MariaDB on Ubuntu 26.04
+* Add multi-statement SQL query support when executing inline in MySQL/MariaDB module
+* Add support for ext4 hidden inode quota mode
+* Add used space and usage percentage reporting for ZFS in the dashboard
+* Add mass enable and disable buttons for status monitors in the System and Server Status module
+* Update tiny ACME client to the latest version
+* Update DHCP default config for openSUSE 16 [#2678](https://github.com/webmin/webmin/issues/2678)
+* Fix to prevent bypassing two-factor authentication in RPC requests
+* Fix session cookies to use safer defaults
+* Fix handling of connections coming through a reverse proxy
+* Fix unsafe mailbox attachment handling in Mailbox module
+* Fix unsafe decoding of Outlook `winmail.dat` attachments
+* Fix Certbot standalone port conflicts
 * Fix to correctly preserve full quoted action parameters in the Fail2Ban jail editor [#2647](https://github.com/webmin/webmin/issues/2647)
+* Fix ZFS to fall back to `df` when disk space cannot be computed from `zpool`
+* Fix to allow toggling process priority and I/O controls on or off
+* Fix issue where disabled email notifications were still being processed
+* Update Authentic theme to the latest version with various improvements and fixes:
+  - Add option to control corner roundness for the menu, content area and right-side slider
+  - Change the content area to use rounded corners and a margin by default
+  - Fix message of the day display in login page correctly [webmin#2555](https://github.com/webmin/webmin/issues/2685)
+  - Fix tooltip visibility in dark palette
+  - Fix session login button spinner
+  - Fix various button styling issues (active state, tiny buttons, airy buttons, stack position)
 
 #### 2.630 (March 24, 2026)
 * Add improvements to user input validation across all modules