docs: update Unraid OS 7.2.5-rc.2 changelog (#462)

## Summary
- Change the 7.2.5 release note title to 7.2.5-rc.2 dated 2026-04-20.
- Make the rc.2 delta explicit: the Unraid API 4.32.3 update, Linux
kernel update, and rare-crash mitigation are new from rc.1.
- Keep carried-forward Docker, storage, WebGUI, API registration-state,
and base distro entries under an "Included from rc.1" section.

## Validation
- pnpm exec remark docs/unraid-os/release-notes/7.2.5.md --quiet --frail
- git diff --check

Full build intentionally not run, per repo guidance for routine docs
validation.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Documentation**
* 7.2.5-rc.2 release notes updated to reflect a Docker + Linux kernel
security/stability release.

* **Security**
  * runc fixes for CVE-2025-31133, CVE-2025-52565, CVE-2025-52881.
  * Linux kernel X.509 fix for CVE-2026-31430.

* **Bug Fixes**
  * Rare system crash mitigation added.
  * Kernel updated to 6.12.82-Unraid.

* **Updates**
  * Unraid API reference updated to dynamix.unraid.net 4.32.3.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: elibosley

docs/unraid-os/release-notes/7.2.5.md

@@ -1,6 +1,8 @@
-# Version 7.2.5-rc.1 2026-04-15
+# Version 7.2.5-rc.2 2026-04-20
 
-This release updates Docker for Unraid 7.2.x users and includes targeted fixes for Docker, Tailscale, mover empty-disk workflows, login-page custom case images, and registration state handling.
+This security and bugfix release updates Docker and the Linux kernel for Unraid 7.2.x users. It also includes targeted fixes for Docker, Tailscale, mover empty-disk workflows, login-page custom case images, and registration state handling.
+
+The Docker update includes runc fixes for CVE-2025-31133, CVE-2025-52565, and CVE-2025-52881.
 
 This release is recommended for all 7.2.x users.
 
@@ -16,7 +18,24 @@ For other known issues, see the [7.2.4 release notes](/unraid-os/release-notes/7
 
 If rolling back earlier than 7.2.4, also see the [7.2.4 release notes](/unraid-os/release-notes/7.2.4/).
 
-## Changes vs. [7.2.4](/unraid-os/release-notes/7.2.4/)
+## Changes from rc.1
+
+Only the Unraid API update, Linux kernel update, and rare-crash mitigation are new in rc.2.
+
+### Unraid API
+
+- dynamix.unraid.net 4.32.3 - [see changes](https://github.com/unraid/api/releases)
+
+### Linux kernel
+
+- version 6.12.82-Unraid
+- Security: Pick up upstream fixes for CVE-2026-31430, a Linux X.509 out-of-bounds access issue triggered by specially crafted certificates.
+
+### System
+
+- Fix: Add a mitigation for a rare crash.
+
+## Included from rc.1
 
 ### Containers / Docker
 
@@ -34,13 +53,8 @@ If rolling back earlier than 7.2.4, also see the [7.2.4 release notes](/unraid-o
 
 ### Unraid API
 
-- Updated to version v4.32.2 - [release notes](https://github.com/unraid/api/releases)
 - Fix: Improve registration-state refresh after license updates so the WebGUI reflects the current license state more reliably.
 
-### Linux kernel
-
-- version 6.12.54-Unraid (no change)
-
 ### Base distro updates
 
 - docker: version 27.5.1 -> 29.3.1 (CVE-2026-34040, CVE-2026-33997, CVE-2026-33748, CVE-2026-33747, CVE-2025-61729, CVE-2025-61727, CVE-2025-31133, CVE-2025-52565, CVE-2025-52881, CVE-2025-54388, CVE-2024-45341, CVE-2024-45336, CVE-2025-27144)