Revert "Add thumbnail column to task"

This reverts commit b4b6ef6fd4f0beb9476007391423b759876e6979.
Revert "Fill the new thumbnail field in task entity"

This reverts commit f40a6c9805415efa28fb404669c9faed49fb365a.
Revert "Fix missing break"

This reverts commit 162beecc7c890c5e434bb817130bd73d798692e2.
Revert "Add Preview field to jobs"

This reverts commit 3b5fd5ab8c5a64b2a9a2f832e6363eb523380699.