Root cause: Promise.all() waits for ALL promises, so a single hung/slow request
blocks the entire batch. With 5001 promises and 16 concurrent limit, timeouts
cause cascading delays that appear as 'scan stopped'.
Fix:
- Extract processSingleActivity() helper function
- Use Promise.allSettled() instead of Promise.all()
- Each promise handles its own success/error counting
- Prevents single hung promise from blocking entire scan
Impact: Scan should now complete all 5001 IDs without getting stuck
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