Make 2FA remember duration configurable

.env.template

@@ -587,6 +587,9 @@
 ## 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: 3650).
+# 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

src/auth.rs

@@ -473,13 +473,34 @@ pub fn generate_2fa_remember_claims(device_uuid: DeviceId, user_uuid: UserId) ->
     let time_now = Utc::now();
     TwoFactorRememberClaims {
         nbf: time_now.timestamp(),
-        exp: (time_now + TimeDelta::try_days(30).unwrap()).timestamp(),
+        exp: two_factor_remember_expiration(time_now, CONFIG.two_factor_remember_days()),
         iss: JWT_2FA_REMEMBER_ISSUER.to_string(),
         sub: device_uuid,
         user_uuid,
     }
 }
 
+fn two_factor_remember_expiration(time_now: DateTime<Utc>, remember_days: i64) -> i64 {
+    (time_now + TimeDelta::try_days(remember_days).expect("TWO_FACTOR_REMEMBER_DAYS is validated")).timestamp()
+}
+
+#[cfg(test)]
+mod two_factor_remember_tests {
+    use chrono::TimeZone;
+
+    use super::*;
+
+    #[test]
+    fn expiration_uses_configured_number_of_days() {
+        let time_now = Utc.with_ymd_and_hms(2026, 7, 14, 12, 0, 0).unwrap();
+
+        assert_eq!(
+            two_factor_remember_expiration(time_now, 45),
+            Utc.with_ymd_and_hms(2026, 8, 28, 12, 0, 0).unwrap().timestamp()
+        );
+    }
+}
+
 #[derive(Debug, Serialize, Deserialize)]
 pub struct BasicJwtClaims {
     // Not before

src/config.rs

@@ -705,6 +705,8 @@ make_config! {
         /// Disable Two-Factor remember |> Enabling this would force the users to use a second factor to login every time.
         /// Note that the checkbox would still be present, but ignored.
         disable_2fa_remember:   bool,   true,   def,    false;
+        /// Two-Factor remember duration |> Number of days before a remembered Two-Factor login expires (min: 1, max: 3650).
+        two_factor_remember_days: i64,  true,   def,    30;
 
         /// Disable authenticator time drifted codes to be valid |> Enabling this only allows the current TOTP code to be valid
         /// TOTP codes of the previous and next 30 seconds will be invalid.
@@ -1209,6 +1211,10 @@ fn validate_config(cfg: &ConfigItems, on_update: bool) -> Result<(), Error> {
         err!("`INVITATION_EXPIRATION_HOURS` has a minimum duration of 1 hour")
     }
 
+    if !(1..=3650).contains(&cfg.two_factor_remember_days) {
+        err!("`TWO_FACTOR_REMEMBER_DAYS` must be between 1 and 3650 days")
+    }
+
     // Validate schedule crontab format
     if !cfg.send_purge_schedule.is_empty() && cfg.send_purge_schedule.parse::<Schedule>().is_err() {
         err!("`SEND_PURGE_SCHEDULE` is not a valid cron expression")