feat: restore is_rolled_back on apps table and rollback UI badge

The cleanup branch incorrectly removed the is_rolled_back column from
the apps table and the dashboard's rollback badge. This restores it:
- Schema: keep is_rolled_back boolean on apps table
- Go handlers: rollback sets true, promote/deploy set false
- Dashboard: restore "Rolled Back" badge and warning row styling
- Docs: update workflow description to match explicit flag approach

Author: Flo4604

cmd/dev/seed/local.go

@@ -137,6 +137,7 @@ func seedLocal(ctx context.Context, cmd *cli.Command) error {
 			Name:             projectName,
 			Slug:             "default",
 			LiveDeploymentID: sql.NullString{},
+			IsRolledBack:     false,
 			DepotProjectID:   sql.NullString{},
 			DeleteProtection: sql.NullBool{Valid: false, Bool: false},
 			CreatedAt:        now,