GitLab

- Move IncrementRPM after Forward success to prevent phantom RPM
  consumption during account switch retries
- Add base_rpm input sanitization (clamp to 0-10000) in Create/Update
- Add WindowCost scheduling checks to legacy path sticky sessions
  (4 check sites + 4 prefetch sites), fixing pre-existing gap
- Clean up rpm_strategy/rpm_sticky_buffer when disabling RPM in
  BulkEditModal (JSONB merge cannot delete keys, use empty values)
- Add json.Number test cases to TestGetBaseRPM/TestGetRPMStickyBuffer
- Document TOCTOU race as accepted soft-limit design trade-off