fix(logs): stop build-log polling once build finishes

The build-logs tab kept polling every 5s and showing the auto-refresh
indicator even after the build reached a terminal state. Gate both on
the build still being in progress, and label a completed build as
"done" instead of the misleading "running" status.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/i18n/dictionaries/en.ts

@@ -233,6 +233,7 @@ const en: Dictionary = {
       buildPending: 'Build is pending...',
       noDeployments: 'No deployments yet. Deploy your app to see build logs.',
       noBuildLogs: 'No build logs available for this deployment.',
+      buildDone: 'Done',
     },
     externalAccess: {
       title: 'External access',