fix(cache_metrics): clamp negative total values before writing to DB

[ArjunJagdale]

Fixes #2495

This PR ensures that total values stored in the cache metrics collection are never negative.

Specifically:

• In collect_cache_metrics(), we now clamp the total to max(total, 0) before calling .upsert_one()
• A warning is logged if a negative value is detected and corrected

While the total originates from get_responses_count_by_kind_status_and_error_code(), this fix guarantees data consistency at the write layer.