Flask integration does not create transactions when called via Flask.wsgi_app (like Connexion 3.x)

### How do you use Sentry?

Sentry Saas (sentry.io)

### Version

2.34.1
### Steps to Reproduce

1. `pip install 'connexion[flask]==3.*' sentry_sdk gunicorn uvicorn`
2. Create `app.py` and `openapi.yaml` as below

openapi.yaml

```yaml
openapi: 3.0.0
info:
title: Test
version: 1.0.0
paths:
/api:
get:
operationId: app.test_op
responses:
'200':
description: Test response
content:
application/json:
schema:
type: string
```


app.py

```python
import connexion
import sentry_sdk

def debug(evt, hint):
print(evt["contexts"]["trace"]["trace_id"])
return evt

sentry_sdk.init(debug=True, before_send=debug, traces_sample_rate=1.0)

def test_op():
return "Hello world"

if __name__ == "__main__":
app = connexion.FlaskApp("app")
app.add_api("openapi.yaml")
app.run(port=5000)
```

3. `python app.py`
4. Access http://localhost:5000/api a few times

pip freeze --all

```
a2wsgi==1.10.10
anyio==4.10.0
asgiref==3.9.1
attrs==25.3.0
blinker==1.9.0
certifi==2025.8.3
charset-normalizer==3.4.3
click==8.2.1
connexion==3.2.0
distlib==0.3.9
filelock==3.18.0
Flask==3.1.1
gunicorn==23.0.0
h11==0.16.0
httpcore==1.0.9
httpx==0.28.1
idna==3.10
inflection==0.5.1
itsdangerous==2.2.0
Jinja2==3.1.6
jsonschema==4.25.0
jsonschema-specifications==2025.4.1
MarkupSafe==3.0.2
packaging==25.0
pip==25.0.1
platformdirs==4.3.7
python-multipart==0.0.20
PyYAML==6.0.2
referencing==0.36.2
requests==2.32.4
rpds-py==0.27.0
sentry-sdk==2.34.1
sniffio==1.3.1
starlette==0.47.2
typing_extensions==4.14.1
urllib3==2.5.0
uvicorn==0.35.0
virtualenv==20.29.3
Werkzeug==3.1.3
```

### Expected Result

Trace ID changes for each request, as transactions are created

### Actual Result

Each request prints the same trace_id (and all events end up in the same transaction)