feat(submissions): instructor-facing enhancements

[adi-herwana-nus]

• hide "block submissions after deadline" switch when no end_at is configured
• instructors can always create submissions for testing
• (instructor) submissions created after deadline have no deadline enforcement

[Copilot]

Pull request overview

This PR refines assessment submission deadline behavior to better support instructor workflows: it hides a deadline-related toggle when no end date exists, ensures staff can still initiate test attempts after deadlines, and prevents automatic deadline enforcement for those staff-created “post-deadline” attempts while preserving time-limit enforcement.

Changes:

• Update Course::Assessment::Submission#force_submit_at to ignore an already-passed submission deadline when the submission was created after that deadline (e.g., staff test runs), while still enforcing time limits.
• Align instructor-facing UI/API behavior so staff managers aren’t shown a “closed” state solely due to a passed deadline when they can still create attempts.
• Add/adjust specs to distinguish “started before deadline” vs “created after deadline” cases for force-submit scheduling and edit fail-safes.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
spec/models/course/assessment/submission_force_submit_spec.rb	Adds coverage for post-deadline-created submissions (deadline ignored) vs pre-deadline-created submissions (deadline enforced), plus time-limit behavior.
spec/jobs/course/assessment/submission/schedule_expiring_submissions_job_spec.rb	Ensures past-due scheduling tests model “begun before deadline” after the new force-submit logic.
spec/jobs/course/assessment/submission/force_submit_timed_submission_job_spec.rb	Adjusts setup so the tested submission is created before the passed deadline to remain force-submittable.
spec/controllers/course/assessment/submission/late_submission_spec.rb	Adds coverage ensuring staff-created post-deadline test attempts are not force-submitted by the edit fail-safe.
client/app/bundles/course/assessment/components/AssessmentForm/index.tsx	Hides the late-submission toggle when there’s no end date (since it has no effect).
app/views/course/assessment/assessments/_assessment_actions.json.jbuilder	Prevents “closed” status for staff managers when the deadline has passed, matching create authorization behavior.
app/models/course/assessment/submission.rb	Implements the core behavior change: ignore already-passed deadline when created_at > deadline, still applying time limit if present.

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