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

options/locale/locale_en-US.json

@@ -3644,6 +3644,7 @@
   "actions.runners.id": "ID",
   "actions.runners.name": "Name",
   "actions.runners.owner_type": "Type",
+  "actions.runners.availability": "Availability",
   "actions.runners.description": "Description",
   "actions.runners.labels": "Labels",
   "actions.runners.last_online": "Last Online Time",
@@ -3659,6 +3660,12 @@
   "actions.runners.update_runner": "Update Changes",
   "actions.runners.update_runner_success": "Runner updated successfully",
   "actions.runners.update_runner_failed": "Failed to update runner",
+  "actions.runners.enable_runner": "Enable this runner",
+  "actions.runners.enable_runner_success": "Runner enabled successfully",
+  "actions.runners.enable_runner_failed": "Failed to enable runner",
+  "actions.runners.disable_runner": "Disable this runner",
+  "actions.runners.disable_runner_success": "Runner disabled successfully",
+  "actions.runners.disable_runner_failed": "Failed to disable runner",
   "actions.runners.delete_runner": "Delete this runner",
   "actions.runners.delete_runner_success": "Runner deleted successfully",
   "actions.runners.delete_runner_failed": "Failed to delete runner",