tools: add send-test-push for one-shot Asynq push verification

Tiny CLI that enqueues a notification:send_push task into Redis. The
worker picks it up and routes through internal/push/Client.SendToAll —
which is exactly the path used by HandleSmartReminder, HandleDailyDigest,
and any other in-process push, so a successful round-trip here proves the
production push pipeline end-to-end without waiting for the next cron tick.

Requires Redis to be reachable. Easiest path:

  kubectl -n honeydue port-forward svc/redis 6379:6379

  go run ./cmd/send-test-push --user-id 6 --title "..." --message "..."

The worker logs `Sending push notification...` followed by the APNs
batch result; failure modes (BadDeviceToken, circuit breaker, etc.)
surface as the same error_message rows the existing notif-diag tool
already reports on.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -10,6 +10,7 @@ bin/
 /admin
 /admin-reset
 /notif-diag
+/send-test-push
 !admin/
 *.exe
 *.exe~