feat(actions): Add Actions API endpoints for workflow run management and logs (#35382)

Implements the missing REST API endpoints for Actions workflow run
management:

1. `POST /actions/runs/{run}/cancel` cancels a run and its jobs, `409`
when it already finished
1. `POST /actions/runs/{run}/approve` approves a run awaiting approval,
idempotent, `409` when it never awaited one
1. `GET /actions/runs/{run}/logs` downloads the latest attempt's job
logs as a zip archive

`ActionWorkflowRun` gains `created_at`, `updated_at` and the `jobs_url`,
`logs_url`, `artifacts_url`, `cancel_url` and `rerun_url` fields, and
now always emits `conclusion` and `head_branch`.

Cancellation is shared with the web handler in `services/actions`.

Fixes https://github.com/go-gitea/gitea/issues/35176
Fixes https://github.com/go-gitea/gitea/issues/36554

---------

Co-authored-by: Claude Sonnet 4.6 <claude-sonnet-4-6@anthropic.com>
Co-authored-by: OpenCode Agent <opencode@rossgolder.com>
Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/util/truncate.go

@@ -130,3 +130,17 @@ func TruncateRunes(str string, limit int) string {
 	}
 	return string([]rune(str)[:limit])
 }
+
+// TruncateStringBytes returns a truncated string with given byte limit,
+// it returns input string if its byte length doesn't exceed the limit.
+func TruncateStringBytes(str string, limit int) string {
+	l := 0
+	for i, r := range str {
+		rl := utf8.RuneLen(r)
+		if l+rl > limit {
+			return str[:i]
+		}
+		l += rl
+	}
+	return str
+}