GitLab

- Add 5th error filter switch IgnoreInsufficientBalanceErrors to suppress
  upstream insufficient balance / insufficient_quota errors from ops log
- Extract hardcoded error strings into package-level constants for
  shouldSkipOpsErrorLog, normalizeOpsErrorType, classifyOpsPhase, and
  classifyOpsIsBusinessLimited
- Define ErrNoAvailableAccounts sentinel error and replace all
  errors.New("no available accounts") call sites
- Update tests to use require.ErrorIs with the sentinel error

- Fix bulk edit: send 0 instead of null/NaN to clear load_factor
- Fix edit modal: explicit NaN check instead of implicit falsy
- Fix create modal: use ?? instead of || for load_factor
- Add load_factor upper limit validation (max 10000)
- Add //go:build unit tag and self-contained intPtrHelper in test
- Add design intent comments on WaitPlan.MaxConcurrency