Backend sync effect (useEffect mount) was unconditionally
replacing mgr.presets with data.presets, destroying:
- Frontend-only default presets (12 vs backend's 7)
- User-defined presets in localStorage not yet synced to backend
Fix: merge backend presets by id — keep all local presets,
append any backend presets whose id doesn't exist locally.
User presets + frontend defaults are never lost.
3dtours
6a46b1ffe4