[JayHome137]

Problem

Local business-limited requests such as Insufficient account balance were written into Channel Monitor V2 error_requests, so the UI reported low upstream availability even when the request never reached an upstream account.

Change

• Carry is_business_limited into the error aggregation CTE.
• Exclude business-limited rows from SLA request/error and per-user metrics while retaining them in the error breakdown.
• Classify insufficient account balance as quota_or_balance in Go and SQL taxonomies.
• Add regression coverage for the SQL filter and taxonomy parity.

Validation

• go test ./internal/service -count=1
• go test ./internal/repository -count=1
• Targeted Channel Monitor V2 tests
• git diff --check

Target branch: sub2api-custom.