test : add unit tests for finding_intelligence build_asset_summary function

[tmdeveloper007]

Summary of What Needs to be Done:
The backend/secuscan/finding_intelligence.py module's build_asset_summary function is a public, pure function that is not covered by the existing test_finding_intelligence.py tests (which only cover build_finding_groups and build_scan_diff). This function merges service inventory with finding data to produce an asset-level summary. Adding unit tests ensures correctness of severity ranking, asset grouping, and sorting logic.

Changes that Need to be Made:
Add test cases to testing/backend/unit/test_finding_intelligence.py (extend existing file):

• build_asset_summary returns one entry per unique asset_id
• Services are grouped under their corresponding assets
• Findings increment finding_count per asset
• Validated findings increment validated_count
• Severity is correctly escalated to the highest finding severity
• Assets are sorted by severity desc, then finding_count desc
• Empty inputs return empty list

Import: from backend.secuscan.finding_intelligence import build_asset_summary
Run: python3 -m pytest testing/backend/unit/test_finding_intelligence.py -v --noconftest

Impact that it would Provide:

• Prevents regressions in asset summary aggregation logic
• Ensures severity escalation and sorting work correctly
• Increases coverage for a function used in dashboard and reporting

Note: This task is being handled by tmdeveloper007 — please assign to that account when picking it up.