26.3.0-rc0 prep (besu-eth#10017)

* Update GitHub repository references from hyperledger/besu to besu-eth/besu

Prepare for org migration by updating all GitHub repository references
to the new besu-eth organization. External service URLs (Docker Hub,
Artifactory, docs site, homebrew, wiki, email) are intentionally left
unchanged for a separate rebranding phase.

Closes besu-eth#9911 (Phase 1 final step)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: jflo <justin+github@florentine.us>

* Update platform/build.gradle

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Justin Florentine <justin+github@florentine.us>

* updated changelog and version

Signed-off-by: jflo <justin+github@florentine.us>

---------

Signed-off-by: jflo <justin+github@florentine.us>
Signed-off-by: Justin Florentine <justin+github@florentine.us>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

CHANGELOG.md

@@ -1,6 +1,9 @@
 # Changelog
 
-## Unreleased
+## 26.3.0
+
+### Repository Migration
+- The Besu repository has moved from `hyperledger/besu` to `besu-eth/besu`. GitHub automatically redirects all existing links from the old location.
 
 ### Repository Migration
 - The Besu repository has moved from `hyperledger/besu` to `besu-eth/besu`. GitHub automatically redirects all existing links from the old location.