Update env template file (#4276)

* update env template to fit the config.rs

* Categorize env template settings

* Fix a wrong setting

* Fix wrong icon redirect code

* Fix ICON_DOWNLOAD_TIMEOUT default value

Co-authored-by: Daniel <[email protected]>

* Move related settings together.
Merge Yubikey, Duo, Email 2FA sections into one.
Other minor fixes.

* Minor fix of some settings position

* Add some comment

* Minor fix.

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Co-authored-by: Daniel <[email protected]>