-- Add a backlink from task_task to task_tasktemplate so that tasks created from
-- a template (e.g. onboarding suggestions or the template catalog) can be
-- reported on and filtered. Nullable — user-created custom tasks remain unset.

ALTER TABLE task_task
    ADD COLUMN IF NOT EXISTS task_template_id BIGINT NULL;

CREATE INDEX IF NOT EXISTS idx_task_task_task_template_id
    ON task_task (task_template_id);

-- Deferred FK — not enforced at the DB level because task_tasktemplate rows
-- may be renamed/retired; application code is the source of truth for the
-- relationship and already tolerates nil.