phsl / new-api

🚀 chore(ui): Refactor UpstreamRatioSync with conflict-modal component, performance hooks & cleanup (#1286)

WHAT’S NEW
• Extracted reusable ConflictConfirmModal for clearer JSX hierarchy
• Added detailed conflict detection & confirmation flow before syncing options
• Refactored state-heavy callbacks (`selectValue`, `performSync`) with `useCallback` to avoid unnecessary renders
• Introduced build-time constants (later removed unused export) and unified helper utilities
• Ensured final ratios are rebuilt accurately before API `PUT`, fixing “value not updated” bug
• Enhanced UI hints: warning icon on conflict, multiline billing info, mobile-friendly modal size
• General code cleanup: removed dead variables, adopted early returns, improved comments

WHY
Improves maintainability, user clarity when billing-type collisions occur, and guarantees data consistency after synchronisation.