Update CVS ingestion flow to create vulnerability findings for each sbom_occurrence_ref with applicable Package Advisory
## Summary
The CVS (Continuous Vulnerability Scanning) ingestion flow needs to be updated to ensure that a vulnerability finding is created for each `sbom_occurrence_ref` that is associated with an `sbom_occurrence` where an applicable Package Advisory has been identified.
## Problem
Currently, the CVS ingestion flow may not be creating vulnerability findings for all branch-specific SBOM occurrences when Package Advisories are matched. This is critical for supporting dependencies across multiple branches.
## Proposed Solution
Update the CVS ingestion flow to:
- Identify all `sbom_occurrence_ref` records associated with an `sbom_occurrence` that has a matching Package Advisory
- Create a vulnerability finding for each of these references to ensure branch-specific vulnerability tracking
- Ensure the findings are properly linked to their respective branches/refs
## Acceptance Criteria
- [ ] CVS ingestion creates vulnerability findings for each `sbom_occurrence_ref` when a Package Advisory matches
- [ ] Findings are correctly associated with their respective branches
- [ ] No duplicate findings are created for the same vulnerability on the same ref
- [ ] Database queries are optimized to handle this at scale
## Related
Epic: #18681
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