[Blocker] Fix: Prevent 'Invalid Date' display on task pages

## GitHub Update **Repository:** [MKWcorp/berkomunitas](https://github.com/MKWcorp/berkomunitas) **Author:** multimediadrw **Date:** 2/7/2026, 10:29:55 AM **Commit:** [`e57ae13`](https://github.com/MKWcorp/berkomunitas/commit/e57ae13024316d060860b221ac0013041486b411) ### Commit Message Fix: Prevent 'Invalid Date' display on task pages - Add date validation (isNaN check) before formatting dates - Validate tanggal_selesai, completion_timestamp, and post_timestamp - Show fallback text instead of 'Invalid Date' when date is invalid - Improves user experience on task detail and task list pages Fixes issue where null/undefined/invalid dates showed as 'Invalid Date' --- _This story was imported from historical commits._