Remove action runners on user deletion (#27902) (#27908)

Backport #27902 by @earl-warren

- On user deletion, delete action runners that the user has created.
- Add a database consistency check to remove action runners that have
nonexistent belonging owner.
- Resolves https://codeberg.org/forgejo/forgejo/issues/1720

(cherry picked from commit 009ca7223dab054f7f760b7ccae69e745eebfabb)

Co-authored-by: Earl Warren <109468362+earl-warren@users.noreply.github.com>
Co-authored-by: Gusted <postmaster@gusted.xyz>

modules/doctor/dbconsistency.go

@@ -6,6 +6,7 @@ package doctor
 import (
 	"context"
 
+	actions_model "code.gitea.io/gitea/models/actions"
 	activities_model "code.gitea.io/gitea/models/activities"
 	"code.gitea.io/gitea/models/db"
 	issues_model "code.gitea.io/gitea/models/issues"
@@ -151,6 +152,12 @@ func checkDBConsistency(ctx context.Context, logger log.Logger, autofix bool) er
 			Fixer:        activities_model.FixActionCreatedUnixString,
 			FixedMessage: "Set to zero",
 		},
+		{
+			Name:         "Action Runners without existing owner",
+			Counter:      actions_model.CountRunnersWithoutBelongingOwner,
+			Fixer:        actions_model.FixRunnersWithoutBelongingOwner,
+			FixedMessage: "Removed",
+		},
 	}
 
 	// TODO: function to recalc all counters