[Coder] Schema update

[ariga-bot]

Backward-incompatible change: renamed column public.workspaces.last_used_at to last_activity_at in the CREATE TABLE statement. Applications referencing last_used_at will break until updated.

[github-actions]

atlas migrate lint on dirs/coder/migrations

Status	Step	Result
	1 new migration file detected	20260401153314.sql
	ERD and visual diff generated	View Visualization
	Analyze 20260401153314.sql 1 reports were found in analysis	Destructive changes detected Dropping non-virtual column "last_used_at" (DS103)
Read the full linting report on Atlas Cloud

[github-actions]

Caution

destructive changes detected
Dropping non-virtual column "last_used_at" DS103

Add a pre-migration check to ensure column "last_used_at" is NULL before dropping it

Suggested change

	-- Modify "workspaces" table
	ALTER TABLE "workspaces" DROP CONSTRAINT "workspaces_last_used_at_not_before_sentinel", ADD CONSTRAINT "workspaces_last_used_at_not_before_sentinel" CHECK (last_activity_at >= '0001-01-01 00:00:00'::timestamp without time zone), DROP COLUMN "last_used_at", ADD COLUMN "last_activity_at" timestamp NOT NULL DEFAULT '0001-01-01 00:00:00';
	-- atlas:txtar
	-- checks/destructive.sql --
	-- atlas:assert DS103
	SELECT NOT EXISTS (SELECT 1 FROM "public"."workspaces" WHERE "last_used_at" IS NOT NULL) AS "is_empty";
	-- migration.sql --
	-- Modify "workspaces" table
	ALTER TABLE "workspaces" DROP CONSTRAINT "workspaces_last_used_at_not_before_sentinel", ADD CONSTRAINT "workspaces_last_used_at_not_before_sentinel" CHECK (last_activity_at >= '0001-01-01 00:00:00'::timestamp without time zone), DROP COLUMN "last_used_at", ADD COLUMN "last_activity_at" timestamp NOT NULL DEFAULT '0001-01-01 00:00:00';

Ensure to run atlas migrate hash --dir "file://dirs/coder/migrations" after applying the suggested changes.