refactor(actions): small cleanups across models, services and routers (#39722)

Collection of small, behaviour-preserving cleanups in the Actions code.

- Fix log and error prefixes that named non-existent or wrong functions,
and wrap errors with `%w` so `errors.Is` keeps working.
- Remove unused code.
- Rely on `ctx.ServerError` / `ctx.APIErrorAuto`, which already map
`util.ErrNotExist` and friends, instead of equivalent hand-written
switches.
- Load runs referenced by commit statuses with one query instead of one
per run (used on every PR view); the result order is now stable.
- Encode an event's payload once instead of up to three times.
- Share the duplicated runner-token "get or create" logic and the
"notify and emit" call pair.
- Simplify `ToActionArtifact` / `ToActionRunner` signatures.

---------

Signed-off-by: bircni <bircni@icloud.com>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/actions/run.go

@@ -296,7 +296,9 @@ func GetRunByRepoAndID(ctx context.Context, repoID, runID int64) (*ActionRun, er
 }
 
 func GetRunsByRepoAndID(ctx context.Context, repoID int64, runIDs []int64) (runs []*ActionRun, err error) {
-	err = db.GetEngine(ctx).In("id", runIDs).Where("repo_id=?", repoID).OrderBy("id").Find(&runs)
+	if len(runIDs) > 0 {
+		err = db.GetEngine(ctx).In("id", runIDs).Where("repo_id=?", repoID).OrderBy("id").Find(&runs)
+	}
 	return runs, err
 }