File upload improvements: "/ufsu" api mode, no interrupts disabling, cleaner confirmation page

[s-hadinger]

Description:

File upload improvements:

• now you can use directly "/ufsu" API to upload a file without displaying the File Manager page first
• no interrupts disabling when file upload, to avoid Multicast reconnects
• GPIO Viewer button is not shown anymore when file upload is complete

Should I mention that it was all done by Claude Opus 4.6?

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.8
• The code change is tested and works with Tasmota core ESP32 V.3.1.10
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass

[eku]

Should I mention that it was all done by Claude Opus 4.6?

Did it also the tests on real hardware?

[s-hadinger]

Should I mention that it was all done by Claude Opus 4.6?

Did it also the tests on real hardware?

No, I did