Can't create push monitor via API

**Describe the bug**
Impossible to create a push monitor via API because it doesn't manage the token generation.

**Database**
- postgresql

**To Reproduce**
Steps to reproduce the behavior:
```
tmp_config=$(jq -nc \
'{
"pushToken": ""
}')

# construction du json final
payload=$(jq -nc \
--arg name "$name" \
--arg config "$tmp_config" \
--arg notification_id "$tmp_notification_id" \
--arg tag_id "$tmp_tag_id" \
'{
"type": "push",
"name": $name,
"interval": 60,
"max_retries": 1,
"retry_interval": 60,
"notification_ids": [$notification_id],
"tag_ids": [$tag_id],
"config": $config,
"resend_interval": 0,
"timeout": 16,
"active": true
}')

curl -X POST "$API_URL" -H "X-API-Key: $API_KEY" -H "Content-Type: application/json" -d "$payload"
```

**Expected behavior**
should generate a token and create the monitor

**Screenshots**
```
{"message":"Invalid monitor configuration: Key: 'PushConfig.PushToken' Error:Field validation for 'PushToken' failed on the 'required' tag","data":null}
```
**Desktop (please complete the following information):**
- OS: Ubuntu 24.04

**Additional context**
Add any other context about the problem here.

Look at the API endpoint for creating monitors, likely in a handler file. Find the push monitor configuration struct and validation logic. The token generation for push monitors needs to be integrated into the create flow when the token is empty. Check existing push monitor creation in the UI to see how tokens are generated there.

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