P2-7: Domain-specific URL preview cards — YouTube shows mqdefault.jpg
thumbnail with ▶ play overlay + title; GitHub shows inline SVG icon +
owner/repo parsed from og:title + star/language info from og:description;
generic cards get a Google favicon when og:image is absent; empty cards
(no title or description) are suppressed entirely
P2-9: Live local time in user profiles — useLocalTime(timezone, hour12)
uses Intl.DateTimeFormat with the user's m.tz IANA zone; updates every
60s; shows clock icon + formatted time + timezone abbreviation (EST/JST
etc.) in dim text; respects existing hour24Clock setting
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
