Account-specific appearance settings

Currently the only account-specific setting is `Blur NSFW` whereas all other settings. including appearance settings, stick for _all_ accounts. It would be fantastic if additional appearance settings (particularly `Post Size`) could be different for each account.

The use case here, at least for Post Size, is that one account may be used primarily for images/media consumption and "Large" would be idea here. Another account that's mostly for news would prefer "Compact." I toggle back and forth for this case quite frequently and having them save per account would be amazing.

The downside is that a user would need to make this change for all accounts assuming they don't like the default, whereas currently they just need to do it once. It would also need to be made clear that these settings changes are only for the current logged in account.

(Thanks for all your wonderful work!)