Add ability for a CRG instance to have a different Default Ruleset to WFTDA

[bullseye555]

Is your feature request related to a problem? Please describe.
A request has come through the Facebook group to be able to have the Post Game Intermission clock disabled by default in the WFTDA ruleset (or, have the ability to turn off the clock at the instance level rather than the ruleset), as the user did not want the clock shown on the stream immediately after a game completed

Describe the solution you'd like
A slightly different suggestion was made, which I believe will have a better quality-of-life improvement and be more useful across roller derby, is to instead be able to set the default ruleset for an instance.
EG: When I start 2025.10 [for example] the first time, the default ruleset is WFTDA - but there is an option in the Rulesets section of /settings/sb_data that allows for a different ruleset to be selected as the Default. This Default would then be the ruleset used for all games that are started/uploaded to CRG after that point

Example (excude the bad screenshot editing)

Describe alternatives you've considered
Having to set the ruleset manually for each game - at larger tournaments that are using non-WFTDA Rulesets for the most/all of the event (eg, JRDA, or tournaments running shortend games during pool stages)

[frank-weinberg]

This doesn't add up.

• The Post Game Intermission Clock is not visible by default, it has to be manually turned on for each game. (There used to be a bug that had it always visible on the overlay but that was ages ago, before there was any setting for it.)
• Not running that clock at all, not even invisibly, would remove the "Unofficial Score" and "Final Score" indicators. That's surely not desirable.
• Either way the setting is not part of the ruleset, so no changes to rulesets would affect it.

That said, marking one ruleset as default should be straightforward to implement and would be useful in other situations. (I would probably use a dropdown instead of a button on each one, however.)