fix(android): prevent screen from turning off during active video calls in example application

[mechtech-mind]

This PR fixes an issue in the Android example application where the device screen turns off automatically during an active video call due to screen timeout.

Problem

During an ongoing LiveKit call on Android, the screen is not kept awake, which leads to:

• Poor user experience during video calls
• Interrupted visibility when no user interaction occurs

Solution

This PR adds native Android window flag handling in MainActivity to ensure the screen remains active while a call is in progress:

• Uses native flags to prevent screen timeout
• Uses native flags as well to handle lock screen visibility

The flags are:

• Enabled when the room is active
• Cleared when the room is disposed

[mechtech-mind]

@hiroshihorie is it ok?

[mechtech-mind]

yeah looks ok

[hiroshihorie]

Left a few small notes. The keep-awake idea makes sense; I think this just needs a little tightening before merge.

[mechtech-mind]

Hi @hiroshihorie,

I have updated the PR as per the changes you suggested:

wrapped the in-call flag calls with Android platform checks
removed the lockscreen/wake-over-screen behavior
removed the unrelated lockfile changes

Thanks again for the review.

[hiroshihorie]

Thanks for the updates. The lockfile and lock screen parts look fixed. I left two small platform notes.

[mechtech-mind]

@hiroshihorie Thanks again for the reviews. I have updated the file as per the requirements. I will make sure to check thoroughly before creating the PR.