Make 2FA remember duration configurable (#7421)

.env.template

@@ -613,6 +613,9 @@
 ## Note that the checkbox would still be present, but ignored.
 # DISABLE_2FA_REMEMBER=false
 ##
+## Number of days before a remembered 2FA login expires (min: 1, max: 90).
+# TWO_FACTOR_REMEMBER_DAYS=30
+##
 ## Authenticator Settings
 ## Disable authenticator time drifted codes to be valid.
 ## TOTP codes of the previous and next 30 seconds will be invalid