Disable catalog refresh timer by default

[olevitt]

Currently Onyxia refresh the catalogs every 5 minutes (see https://github.com/InseeFrLab/onyxia-api?tab=readme-ov-file#catalogs-configuration- catalogs.refresh.ms).
There are some caveats associated with catalog refreshs :

• In case you have multiple API pods, having one refreshed and not the other means they may be desynched resulting in user facing bugs
• Refresh may fail due to a temporary failure in registry
• Refreshing the catalogs and fetching all packages every x minutes may cause some heavy load (see #358 for possible mitigation)
• Periodic refresh on catalogs you don't maintain yourself may result in app breaking unexpectedly

I suggest we disable the refresh by default (setting 0 to catalogs.refresh.ms by default) while still allowing admin to override it. I also suggest we document the caveats.