fix: server overrides user's locale/appearance

[harveyghq]

Close #2767.

Locale usage sequence: storage locale > user locale > server's default locale. (same for appearance)

[boojack]

LGTM otherwise

[harveyghq]

Test: user can change user locale in Preferences / specify a new locale when logging in. Storage locale overrides user locale.

Note: currently when a user doesn't set locale, the default user setting en and follow system will override server's setting.
Maybe in the future, we need to use server's setting locale/appearance as default user setting. (see here)

[boojack]

So the order here should be user setting -> storage -> system setting.

[boojack]

FYI, fixed in 9ffd827

[harveyghq]

But what if a user specifies a new locale in login/sign up page? It will be overriden when the user is logged in. @boojack

I presume that users can configure additional preferences during the login process; otherwise, those buttons would lose their purpose and require users to reconfigure locale/appearance in the settings later.

[harveyghq]

Some scenarios to consider:

• A fresh start: A new user signs up and specifies their preferences on the sign-up page. These preferences should remain unchanged later.
• A signed-up user opens a new browser and logs in without modifying their preference settings on the login page. In this case, the server's default preferences should change to match the user's previously stored preferences.
• A signed-up user specifies new preferences during login, or if they haven't cleared their browser's storage (with last used preferences). These preferences should not be replaced by their preferences stored in the database, and may even require an update to the user's preferences.

So considering above scenarios, I considered using storage > user > server a reasonable one. By giving priority to local storage preferences and only updating them when users specify their preferences during login or when defaults need to be replaced after login, this method ensures that the user's most recent choices take precedence.