feat: mirror to Codeberg via SSH deploy key

Push clean copy (without .forgejo/ and prds/) to Codeberg on
each push to main. Uses SSH deploy key for authentication.

Also bumps kcl-ci to v1.40.0.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.forgejo/kcl-ci/kcl.mod.lock

@@ -4,4 +4,4 @@
     full_name = "kcl-ci_0.0.1"
     version = "0.0.1"
     url = "https://git.wxs.ro/actions/kcl-ci"
-    git_tag = "v1.38.0"
+    git_tag = "v1.40.0"