BUG: Fix workflow run jobs API returning null steps (#36603)

## Problem

`GET /api/v1/repos/{owner}/{repo}/actions/runs/{runId}/jobs` was always
returning `steps: null` for each job.

## Cause

In `convert.ToActionWorkflowJob`, when the job had a `TaskID` we loaded
the task with `db.GetByID` but never loaded `task.Steps`.
`ActionTask.Steps` is not stored in the task row (`xorm:"-"`); it comes
from `action_task_step` and is only filled by `task.LoadAttributes()` /
`GetTaskStepsByTaskID()`. So the conversion loop over `task.Steps`
always saw nil and produced no steps in the API response.

## Solution

After resolving the task (by ID when the caller passes `nil`), we now
load its steps with `GetTaskStepsByTaskID(ctx, task.ID)` and set
`task.Steps` before building the API steps slice. No other behavior is
changed.

## Testing

- New integration test `TestAPIListWorkflowRunJobsReturnsSteps`: calls
the runs/{runId}/jobs endpoint, inserts a task step for a fixture job,
and asserts that the response includes non-null, non-empty `steps` with
the expected step data.
- `make test-sqlite#TestAPIListWorkflowRunJobsReturnsSteps` passes with
this fix.

---------

Co-authored-by: Manav <mdave0905@gmail.com>

services/convert/convert.go

@@ -349,20 +349,29 @@ func ToActionWorkflowJob(ctx context.Context, repo *repo_model.Repository, task
 			}
 		}
 
-		runnerID = task.RunnerID
-		if runner, ok, _ := db.GetByID[actions_model.ActionRunner](ctx, runnerID); ok {
-			runnerName = runner.Name
-		}
-		for i, step := range task.Steps {
-			stepStatus, stepConclusion := ToActionsStatus(job.Status)
-			steps = append(steps, &api.ActionWorkflowStep{
-				Name:        step.Name,
-				Number:      int64(i),
-				Status:      stepStatus,
-				Conclusion:  stepConclusion,
-				StartedAt:   step.Started.AsTime().UTC(),
-				CompletedAt: step.Stopped.AsTime().UTC(),
-			})
+		if task != nil {
+			if task.Steps == nil {
+				task.Steps, err = actions_model.GetTaskStepsByTaskID(ctx, task.ID)
+				if err != nil {
+					return nil, err
+				}
+				task.Steps = util.SliceNilAsEmpty(task.Steps)
+			}
+			runnerID = task.RunnerID
+			if runner, ok, _ := db.GetByID[actions_model.ActionRunner](ctx, runnerID); ok {
+				runnerName = runner.Name
+			}
+			for i, step := range task.Steps {
+				stepStatus, stepConclusion := ToActionsStatus(job.Status)
+				steps = append(steps, &api.ActionWorkflowStep{
+					Name:        step.Name,
+					Number:      int64(i),
+					Status:      stepStatus,
+					Conclusion:  stepConclusion,
+					StartedAt:   step.Started.AsTime().UTC(),
+					CompletedAt: step.Stopped.AsTime().UTC(),
+				})
+			}
 		}
 	}
 
@@ -383,7 +392,7 @@ func ToActionWorkflowJob(ctx context.Context, repo *repo_model.Repository, task
 		Conclusion:  conclusion,
 		RunnerID:    runnerID,
 		RunnerName:  runnerName,
-		Steps:       steps,
+		Steps:       util.SliceNilAsEmpty(steps),
 		CreatedAt:   job.Created.AsTime().UTC(),
 		StartedAt:   job.Started.AsTime().UTC(),
 		CompletedAt: job.Stopped.AsTime().UTC(),