Fix cannot delete people assigned to task

Signed-off-by: gearnode <bryan@frimin.fr>

pkg/coredata/migrations/20250314T111900Z.sql

@@ -0,0 +1,3 @@
+ALTER TABLE tasks DROP CONSTRAINT tasks_assigned_to_fkey;
+ALTER TABLE tasks ADD CONSTRAINT tasks_assigned_to_fkey 
+    FOREIGN KEY (assigned_to) REFERENCES peoples(id) ON DELETE SET NULL;