Add support for configurable update flag strategy with new "same_base" mode that considers base model versions when determining update availability. The strategy is controlled by the "update_flag_strategy" setting.
When strategy is set to "same_base":
- Uses get_records_bulk instead of has_updates_bulk
- Compares model versions against highest local versions per base model
- Provides more granular update detection based on base model relationships
Fallback to existing bulk or individual update checks when:
- Strategy is not "same_base"
- Bulk operations fail
- Records are unavailable
This enables more precise update flagging for models sharing common bases.
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