Video player: fullscreen now hides system status bar, keep screen on while video is playing

[daniele-verducci]

Fix: #17825

This change:

• keeps screen on while playing video
• hides the top status bar when in fullscreen (the system bars were hidden, but the status bar remained visible all the time)

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI (N/A)

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...wncloud/android/ui/preview/PreviewImageActivity.kt	0.00%	2 Missing ⚠️
...loud/android/ui/preview/PreviewPlaybackFragment.kt	0.00%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[github-actions]

📱 QA build

Download	app-qa-debug.apk
QR code	Open the QR code for this download
Commit	bf6a0ce
Version	17830
Available until	7 days after this build

The QA build installs alongside a released Nextcloud app, so you can keep
using your existing install while testing.

Downloading the file requires a GitHub account, so open this link on the
device you want to test on, or transfer the APK to it.

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	25	25
Correctness	52	52
Dodgy code	161	161
Experimental	1	1
Malicious code vulnerability	1	1
Multithreaded correctness	20	20
Performance	28	28
Security	16	16
Total	304	304