added permanent artifact links for latest green builds: /branches/<branch-key>/... serves the latest green build's artifacts (green-only, resolved per request), keepLatestGreen retention protection, permanent artifact-index page, and latestGreenUrl links in the branches view

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main/kotlin/de/hoennig/gittally/commands/InitCommand.kt

@@ -145,6 +145,9 @@ class InitCommand(
               rootDir: ""
               # number of builds to keep per branch
               retentionPerBranch: 3
+              # keep each branch's latest green build beyond the retention count,
+              # so the permanent /branches/<branch-key>/... artifact URLs stay valid while newer builds fail
+              keepLatestGreen: true
 
             # Controls the branch-polling loop.
             watcher: