Prepare 26.3.0 release (#1515)

Sets the release date in the changelog and bumps the version to
26.3.0.

https://claude.ai/code/session_019DNUJVTLqiBdfvjeJd8nu7

Co-authored-by: Claude <noreply@anthropic.com>

CHANGELOG.rst

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4dc46a8..6b694af 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -4,7 +4,7 @@
 Versions are year-based with a strict backward-compatibility policy.
 The third digit is only for regressions.
 
-26.3.0 (UNRELEASED)
+26.3.0 (2026-06-12)
 -------------------
 
 Backward-incompatible changes:

src/OpenSSL/version.py

diff --git a/src/OpenSSL/version.py b/src/OpenSSL/version.py
index 8cb4e28..43aea61 100644
--- a/src/OpenSSL/version.py
+++ b/src/OpenSSL/version.py
@@ -17,7 +17,7 @@
     "__version__",
 ]
 
-__version__ = "26.2.0"
+__version__ = "26.3.0"
 
 __title__ = "pyOpenSSL"
 __uri__ = "https://pyopenssl.org/"