SEB (safe exam browser) Integration

[advay-demo]

This PR introduces support for Safe Exam Browser (SEB) to help us lock down the quiz environment and prevent cheating.

Here’s a quick rundown of what I've added:

• Database updates: Added a few new fields to the Quiz model so instructors can configure SEB settings (like requiring fullscreen, enabling zoom, or checking the config key hash).
• Dynamic Config Generation: Wrote a view that automatically generates and serves the .seb config file based on the quiz's settings so students can easily download it.
• Validation: Updated the quiz launch process to ensure students are actually using the Safe Exam Browser and that their config key hash matches the one expected by the instructor.
• Tests: I also went ahead and added a solid batch of tests for both the view logic and the file generation to make sure everything works smoothly.

[prathamesh920]

please resolve the comments.
run the modified code through PEP8 standards.
remove extra spaces.

[prathamesh920]

After selecting requires SEB and dynamically generating SEB file and saving the quiz, the interface shows no message or changes to the user. Like whether the file is generated or not, is the SEB mode is proper set.

[prathamesh920]

Also, we should give proper instructions to the students.
They should know what steps they need to follow to take the test, including ending the test and exit SEB.

[prathamesh920]

A small loophole:
Right now, our interface allows students to resume an ongoing test if they accidentally close the window,
provided they are still within the overall test time frame.

However, with SEB, a student can simply quit the SEB application mid-test without submitting,
look up answers outside the locked environment and then relaunch SEB to resume their attempt.

For now, I think you can configure an Exit Password for SEB.
Later, the team can come up with a proper policy for handling mid-exam disconnects and re-entry.

[prathamesh920]

Kindly resolve the comments.

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Also, I am slightly concerned with the validation process. We need to validate the actual SEB config/request header correctly. (for dynamic SEB configs too) Because I was able to take the test with different config files for the same test. Try compare_digest for hash comparisons.

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Also, the seb file is a plain text, i am able to modify the configurations. We should encrypt it.

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Also, currently validation happens only at the start of the quiz, but this should ideally happen for each and every request during the quiz.

[prathamesh920]

3000+ files changed!
Pls fix this.