fix: clickhouse entrypoint - backup download is best-effort (server must start regardless)

The previous entrypoint treated clickhouse-backup as required: a download failure
(rate-limit or transient network) caused install_clickhouse_backup to return 1 which
with set -e exited the entrypoint before /entrypoint.sh ran. ClickHouse never started,
the swarm restarted it, the download was retried, amplifying the throttle -> crash-loop
-> deploy timeout (cc-ci Q4.7b).

Fix: install_clickhouse_backup || true — the server starts even if the backup tool
cannot be fetched. Backup/restore degrades until a later restart fetches it.

Also: fix stray trailing quote in backupbot.restore.post-hook; bump
CLICKHOUSE_ENTRYPOINT_VERSION v3->v4 (config content changed).

compose.yml

@@ -82,7 +82,7 @@ services:
         backupbot.backup.path: "/var/lib/clickhouse/backup/events"
         backupbot.backup.post-hook: "rm -rf /var/lib/clickhouse/backup/events"
         backupbot.restore: "true"
-        backupbot.restore.post-hook: clickhouse-backup restore --rm events && rm -rf /var/lib/clickhouse/backup/events"
+        backupbot.restore.post-hook: clickhouse-backup restore --rm events && rm -rf /var/lib/clickhouse/backup/events
 
 volumes:
   db-data: