Backend hangs on campaign activation + Bot returns 500 on publication endpoint

Problem

When activating a campaign (DRAFT → ACTIVE transition) with multiple channels:

Issue 1: Race condition in approval notifications

One of the approval notification tasks failed with:

{'success': False, 'error': 'Campaign in draft or archived'}

Root cause: Celery task send_approval_notification_task was queued via transaction.on_commit() but executed BEFORE the campaign was actually saved as ACTIVE.

Issue 2: Bot endpoint returns 500 Internal Server Error

Publication task publish_campaign_channel_async receives HTTP 502/500 from bot endpoint:

curl -X POST http://localhost:8001/telegram/public-campaign-channel \
  -H 'Content-Type: application/json' -d '{"test":"ping"}'
# Returns: Internal Server Error (HTTP 500)

Bot logs:

WARNING: Invalid HTTP request received.

Celery logs:

[PublishCampaignChannelAsync] Failed to publish: HTTP 502

Impact

• Users don't receive all approval notifications
• Auto-approved channels don't get published (stuck in retry queue)

Expected behavior

1. All approval notifications should be sent reliably
2. Bot endpoint should accept publication requests without 500 errors

Files involved

• web_app/core/admin.py:1811-1925 - campaign activation logic
• web_app/core/tasks.py:1319 - publish_campaign_channel_async task
• bot/main.py - bot webhook endpoint

Campaign ID

9a60db3f-5ee4-4323-ae30-0f752c646015

Logs

See Celery worker logs at 19:51:55 UTC