Move Settings out of the right-side overlay into a left-nav page (page='settings'),
so it opens where you're already looking — no cross-screen mouse travel. The Settings
rail item now sets the page (with active highlight) instead of opening a dialog; the
panel is refactored to an in-flow .glass card (keeps the frosted look over the ambient
backdrop), with the page title shown in the header. Removed the overlay + Esc/backdrop
close path.
Move the modules (Feed/Channels/Playlists/Stats) out of the avatar dropdown into a
persistent left sidebar with icon+label entries; collapses to a thin icon rail
(persisted in localStorage). Account actions (About, Sign out, admin badge) move to a
popover at the sidebar bottom; Settings is a rail entry. Header is now a contextual top
bar (sync status, feed scope + search or page title, language, notifications) — logo and
account menu removed from it. New nav.json strings (HU/EN/DE). First step of Epic N.
