fix(coderd): show correct deletion time in dormancy notification (#26488)

The dormancy notification's "will be automatically deleted in X"
sentence rendered the dormancy threshold instead of the auto-delete
duration. A 30-day threshold rendered as "4 weeks" even when auto-delete
was 90 days; a 60-day threshold rendered as "1 month" with a 7-day
auto-delete. Render the countdown from the auto-delete setting, and skip
the deletion sentence entirely when auto-delete is disabled so the
notification no longer promises a deletion that will never happen.

coderd/database/migrations/000527_dormancy_notification_use_til_delete.down.sql

@@ -0,0 +1,5 @@
+-- Revert to the body left by migration 000518
+-- (000311's wording with the corrected docs URL).
+UPDATE notification_templates SET body_template = E'Your workspace **{{.Labels.name}}** has been marked as [**dormant**](https://coder.com/docs/admin/templates/managing-templates/schedule#dormancy-threshold) due to inactivity exceeding the dormancy threshold.\n\n' ||
+	E'This workspace will be automatically deleted in {{.Labels.timeTilDormant}} if it remains inactive.\n\n' ||
+	E'To prevent deletion, activate your workspace using the link below.' WHERE id = '0ea69165-ec14-4314-91f1-69566ac3c5a0';

coderd/database/migrations/000527_dormancy_notification_use_til_delete.up.sql

@@ -0,0 +1,11 @@
+-- Update the dormant workspace notification body so that the deletion
+-- countdown references a dedicated `timeTilDelete` label, and to only
+-- include the deletion time if the templates' `time_til_dormant_autodelete`
+-- is enabled.
+UPDATE notification_templates SET body_template = E'Your workspace **{{.Labels.name}}** has been marked as [**dormant**](https://coder.com/docs/admin/templates/managing-templates/schedule#dormancy-threshold) due to inactivity exceeding the dormancy threshold.\n\n' ||
+	E'{{ if .Labels.timeTilDelete -}}\n' ||
+	E'This workspace will be automatically deleted in {{.Labels.timeTilDelete}} if it remains inactive.\n\n' ||
+	E'To prevent deletion, activate your workspace using the link below.\n' ||
+	E'{{- else -}}\n' ||
+	E'Activate your workspace using the link below to resume working in it.\n' ||
+	E'{{- end }}' WHERE id = '0ea69165-ec14-4314-91f1-69566ac3c5a0';