Feature: Add per-runner “Disable/Pause” (#36776)

This PR adds per-runner disable/enable support for Gitea Actions so a
registered runner can be paused from picking up new jobs without
unregistering.

Disabled runners stay registered and online but are excluded from new
task assignment; running tasks are allowed to finish. Re-enabling
restores pickup, and runner list/get responses now expose disabled
state.

Also added an endpoint for testing
http://localhost:3000/devtest/runner-edit/enable

<img width="1509" height="701" alt="Bildschirmfoto 2026-02-27 um 22 13
24"
src="https://github.com/user-attachments/assets/5328eda9-e59c-46b6-b398-f436e50ee3da"
/>


Fixes: https://github.com/go-gitea/gitea/issues/36767

models/migrations/migrations.go

@@ -401,6 +401,7 @@ func prepareMigrationTasks() []*migration {
 		newMigration(324, "Fix closed milestone completeness for milestones with no issues", v1_26.FixClosedMilestoneCompleteness),
 		newMigration(325, "Fix missed repo_id when migrate attachments", v1_26.FixMissedRepoIDWhenMigrateAttachments),
 		newMigration(326, "Migrate commit status target URL to use run ID and job ID", v1_26.FixCommitStatusTargetURLToUseRunAndJobID),
+		newMigration(327, "Add disabled state to action runners", v1_26.AddDisabledToActionRunner),
 	}
 	return preparedMigrations
 }