Prepare the 13.4.3 release

* Add cuda-bindings 13.4.3 release notes covering the two recent FFI-audit
  fixes that landed on 13.4.x (#2929 and #2931).
* Back-fill 12.9.9 release notes on the 13.4.x line (from 12.9.x) so the
  docs site — built from the mainline branches — lists them under the
  Version selector.  The 12.9.9 notes get the recent 12.9.x FFI-audit
  backports (#2930 and #2934) appended to their Bugfixes section.
* Add a 13.4.3 entry to cuda_bindings/docs/nv-versions.json and
  cuda_python/docs/nv-versions.json.

Author: leofang

cuda_bindings/docs/nv-versions.json

@@ -3,6 +3,10 @@
         "version": "latest",
         "url": "https://nvidia.github.io/cuda-python/cuda-bindings/latest/"
     },
+    {
+        "version": "13.4.3",
+        "url": "https://nvidia.github.io/cuda-python/cuda-bindings/13.4.3/"
+    },
     {
         "version": "13.4.2",
         "url": "https://nvidia.github.io/cuda-python/cuda-bindings/13.4.2/"