Various QoL fixes for Desktop App (#2999)

* Some ESLint fixes

* Add login/logout signal to API, clear mentions on logout and flush cookies on login/logout

* Fix issue where local and HTTP-only servers would not validate correctly

* Reduce noise of renderer logging, adjust a few local renderer logs to be louder when needed

* Fallback to beginning of hostname for servers that don't change the site name

* Fix Save Image crash

* Update the name for insecure servers too

* Fix test

* Fix lint

* Reduce repetition

api-types/index.ts

@@ -26,6 +26,8 @@ export type DesktopAPI = {
         idleTime: number,
         isSystemEvent: boolean,
     ) => void) => () => void;
+    onLogin: () => void;
+    onLogout: () => void;
 
     // Unreads/mentions/notifications
     sendNotification: (title: string, body: string, channelId: string, teamId: string, url: string, silent: boolean, soundName: string) => Promise<{result: string; reason?: string; data?: string}>;