For any `Screen` that shows on desktop, `title` is "(1) ... - Bluesky" where "(1)" is the unread notification count. The titles are unlocalized and the string "Bluesky" is hardcoded, following the pattern of the rest of the app. Display names and post content are loaded into the title as effects. Tested: * all screens * screen changes / component mounts/unmounts * long posts with links and images * display name set/unset * spamming myself with notifications, clearing notifications * /profile/did:... links * lint (only my changed files), jest, e2e. New utilities: `useUnreadCountLabel`, `bskyTitle`, `combinedDisplayName`, `useSetTitle`. resolves: #626 #599