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

routers/web/repo/actions/actions.go

@@ -317,7 +317,7 @@ func prepareWorkflowList(ctx *context.Context, workflows []WorkflowInfo) {
 			}
 			hasOnlineRunner := false
 			for _, runner := range runners {
-				if runner.CanMatchLabels(job.RunsOn) {
+				if !runner.IsDisabled && runner.CanMatchLabels(job.RunsOn) {
 					hasOnlineRunner = true
 					break
 				}