surface upstream summary/description info of record with only one upstream and empty human fields

**Describe the bug**
When Upstream/Downstream relations in records were introduced potential inconsistency appeared: Downstream records should or should not have own Summary and Description fields.

The OSV-Schema doesn't give explicit guidelines.

If a Downstream record has these fields:
* Pros:
* Everything works as expected
* Cons:
* Data is duplicated. If the data is different it's undetermined how a user should interpret the difference

If a Downstream record has NONE of these fields:
* Pros:
* Database is consistent. Data may be found from the Upstream fields
* Cons:
* The records has no Summary and Description so database entry is not informative. Also OSV-Scanner doesn't extract this information.

**To Reproduce**
1. https://osv.dev/vulnerability/BELL-CVE-2025-40000 is the example of the record having empty fields
2. https://osv.dev/vulnerability/UBUNTU-CVE-2025-40000 is the example where the fields are copied but with the messed up formatting.

**Expected behaviour**
Consistent database and all the fields available in Downsteam records.

**Additional context**
The best solution I see is:
1. propagate the missing info from Upstream record.
2. Make apps like OSV-scanner do the same.