Allow login requirement for expensive pages

[abrain]

Currently, the REQUIRE_SIGNIN_VIEW variable is restricted to a boolean value.

ansible_role_gitea/templates/gitea.ini.j2

Line 148 in 35d5446

REQUIRE_SIGNIN_VIEW = {{ gitea_require_signin | ternary('true', 'false') }}

Recently, Gitea also supports the value 'expensive' to limit the effect that AI crawlers have on system load.

https://docs.gitea.com/administration/config-cheat-sheet#service-service

Although it is marked as experimental, it would be nice to be able to use it.