feat: show live build version in web UI

- /api/version returns version, commitSha, buildDate, trashRetentionDays
- CI passes COMMIT_SHA (full), BUILD_DATE and VERSION (git tag) as
  docker build args; Dockerfile bakes them as env
- sidebar footer shows version/sha linked to the Gitea commit
- admin System tab shows version, commit link, build date, trash retention

Dockerfile

@@ -43,6 +43,13 @@ COPY --from=builder /app/artifacts/toolrate/dist artifacts/toolrate/dist
 ENV NODE_ENV=production
 ENV STATIC_DIR=/app/artifacts/toolrate/dist/public
 
+ARG COMMIT_SHA=""
+ARG BUILD_DATE=""
+ARG VERSION=""
+ENV COMMIT_SHA=${COMMIT_SHA}
+ENV BUILD_DATE=${BUILD_DATE}
+ENV VERSION=${VERSION}
+
 EXPOSE 8080
 
 CMD ["sh", "-c", "pnpm --filter @workspace/db run push-force && node --enable-source-maps artifacts/api-server/dist/index.mjs"]