e8cb086b64
## Summary - Remove 3 completed migration feature flags: `IS_ATTACHMENT_MIGRATED`, `IS_NOTE_TARGET_MIGRATED`, `IS_TASK_TARGET_MIGRATED` — these were already enabled by default for all new workspaces via `DEFAULT_FEATURE_FLAGS` - Delete all upgrade command directories for versions <= 1.18 (`1-16/`, `1-17/`, `1-18/`) along with their module registrations, removing ~6,600 lines of dead migration code - Simplify frontend utility functions (`getActivityTargetObjectFieldIdName`, `getActivityTargetsFilter`, `getActivityTargetFieldNameForObject`, `generateActivityTargetMorphFieldKeys`, `findActivitiesOperationSignatureFactory`) by removing the `isMorphRelation` parameter and always using the morph relation path - Remove feature flag checks from 7 frontend hooks/components that were gating attachment and activity target behavior behind the removed flags - Simplify `buildDefaultRelationFlatFieldMetadatasForCustomObject` server util to always treat attachment, noteTarget, and taskTarget as morph relations without checking feature flags