Fix OU Group Sync documentation: Remove fictional sync mode features

Corrected documentation that incorrectly described user-selectable "Smart Sync"
and "Full Sync" modes and scheduling features that don't exist in the codebase.

Changes:
- Documented actual behavior: first sync only adds (safe mode), subsequent
  syncs mirror OU exactly (adds AND removes members)
- Removed all references to manual sync mode selection
- Removed scheduling documentation (feature doesn't exist)
- Clarified that sync mode is automatic based on whether it's the first sync
- Updated saved configuration management features (resync, export, import)
- Applied corrections to all 3 languages: English, Spanish, Portuguese

Affected files:
- docs/features/ou-group-sync.md
- docs/quickstart.md
- docs/es/features/ou-group-sync.md
- docs/es/quickstart.md
- docs/pt/features/ou-group-sync.md
- docs/pt/quickstart.md

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: Rafael Teodoro