Apply the real frosted .glass surface (blur) to the few large chrome surfaces — the nav
sidebar, the header and all Modal-based dialogs (was glass-card / plain surfaces) — and
enrich the ambient backdrop a touch (three soft accent pools) so the glass has more to
refract app-wide. Popovers (notifications, language, account, add-to-playlist) were
already glass. Bulk feed cards stay glass-card (no per-card blur) for performance; the
existing perf-mode still disables blur. Phase 2 (ambient thumbnail mosaic / bg image +
toggle) deferred to end-of-project polish.
About (in the account menu) shows frontend/backend/database versions + build.
Release Notes renders per-version highlights with a commit-SHA reference; a
dismissible banner appears once after the running build's version changes and
links into the notes. Adds a reusable Modal shell and the release-notes data
(detailed v0.1.0).
