Add batch video upload functionality

[DaniEnsi]

Motivation and Context

Allows lecturers to upload multiple video lectures at once instead of creating them one-by-one. This significantly improves the workflow when importing a batch of pre-recorded lectures (e.g., uploading an entire semester's worth of recordings).

Description

Adds batch video-on-demand (VOD) upload functionality to the lecture creation form, allowing users to create and upload multiple lectures with individual metadata and video files in a single workflow.

Resolves: #1617

Changes:

• Add batch lecture management (add/remove rows) in form data
• Add batch-specific UI in lecture details slide with multiple rows for lecture name and start time
• Add batch-specific media upload slide showing file inputs for each lecture (COMB/PRES/CAM)
• Implement batch upload progress tracking with per-lecture status and per-file progress bars
• Reuse existing createVOD and uploadVODMedia endpoints (no backend changes needed)
• Include automatic rollback on batch upload failure (deletes all created streams if any upload fails)
• Add form validation to ensure all lectures have required metadata before proceeding
• Integrate Flatpickr date/time pickers for batch lecture start times
• Support mixed upload scenarios (some lectures with only COMB, others with PRES+CAM, etc.)

Steps for Testing

Prerequisites:

• Lecturer account
• Access to a course as lecturer
• Multiple video files (mp4 format recommended) for testing

1. Log in as lecturer
2. Navigate to a course management page
3. Click "Create Lecture" button
4. Select "Video Upload" option
5. Enter lecture details for first lecture (name and start time)
6. Click "Add Another Lecture" button to add more rows
7. Fill in details for additional lectures (e.g., 3-5 lectures)
8. Test removing a lecture row using the trash icon
9. Click "Next" to proceed to media upload
10. Upload video files (COMB/PRES/CAM) for each lecture
11. Verify that each lecture shows its own upload section
12. Click "Submit" and observe:
    • Progress indicator shows "Creating streams" phase
    • Progress indicator shows "Uploading" phase with lecture name and file progress
    • Individual file progress bars update for COMB/PRES/CAM
13. After completion, verify all lectures appear in the course lecture list
14. Verify each lecture has correct metadata (name, start time, video files)

Edge cases tested:

• Try to proceed without filling required fields (should show validation message) - ✅
• Try to proceed with empty lecture rows (should show validation message) - ✅
• Test with only 1 lecture (should still work) - ✅
• Simulate upload failure (turned worker off) and verify rollback (all created lectures are deleted) - ✅

Screenshots

TumLive.Batch.Upload.mp4

[DaniEnsi]

Now that I have finished everything I am not sure if this was what you meant by batch upload. I mean this makes it already quicker but how about uploading a folder/zip and allowing the lecturer to change the names afterwards?!

Also just fyi i am pretty new to go, i have decent experience in html (web) but if you have any improvements in general or just style please lmk.

[DaniEnsi]

@joschahenningsen Könnte jemand mal einen Blick hier drauf werfen, nur dass ich weiß was noch geändert werden soll?

[joschahenningsen]

Hey Daniel, sorry, deine PR ist mir durchgerutscht! Ich schaue sie mir heute Abend an, vielen dank für die contribution. 🫶

[joschahenningsen]

You really put lots of effort in this, and I think it's pretty clean! One thing I noticed is, that the "Record Lecture" screen also allows adding multiple lectures, but fails with "All lectures must have a start time!", which it shouldn't.
I'd argue, local recordings should not be possible as batches.

[joschahenningsen]

This is not a concern for us, actually most lectures don't have a title.