Remember login for a month by default (#30150)

Previously, the default was a week.
As most instances don't set the setting, this leads to a bad user
experience by default.

## ⚠️ Breaking

If your instance requires a high level of security,
you may want to set `[security].LOGIN_REMEMBER_DAYS` so that logins are
not valid as long.

---------

Co-authored-by: Jason Song <i@wolfogre.com>
(cherry picked from commit 0d5abe3454c73f11d90d2809af0949a0e0636c22)

custom/conf/app.example.ini

@@ -441,7 +441,7 @@ INTERNAL_TOKEN =
 ;INTERNAL_TOKEN_URI = file:/etc/gitea/internal_token
 ;;
 ;; How long to remember that a user is logged in before requiring relogin (in days)
-;LOGIN_REMEMBER_DAYS = 7
+;LOGIN_REMEMBER_DAYS = 31
 ;;
 ;; Name of the cookie used to store the current username.
 ;COOKIE_USERNAME = gitea_awesome