fix(web): header search dropdown no longer covers the sidebar

Anchor #header-search-overlay to the search bar (position:absolute inside a
relative .header-search-wrap) instead of position:fixed full-viewport width,
so the results drop down at the bar's width and the left sidebar stays visible.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -98,6 +98,10 @@ like Android), concert events become **reliable across web/Android**, and severa
 - **Web importer preview layout** — the SoundCloud track row was missing its grid number-cell, so the
   4-column `.gtrack-item` grid squeezed the cover into 28px and the title into 52px (title wrapped
   one character per line). Added the missing cell.
+- **Header search dropdown covered the sidebar (Web)** — `#header-search-overlay` was
+  `position:fixed; left:0; right:0` (full viewport), overlapping the left sidebar. It's now anchored
+  to the search bar (`position:absolute` inside the wrap), so it drops down at the bar's width and the
+  sidebar stays visible.
 - **Android artist albums incomplete** — `lookupArtistAlbums` filtered to `record_type == "album"`,
   dropping EPs and singles that Deezer (and the web app) show. Now returns all, sorted album → EP →
   single.