Replace the top-nav with a fixed left sidebar + slim content topbar
(the Komga/Audiobookshelf layout), the signature change versus the
conservative tighten-ui branch.
- App shell: .app-sidebar (off-canvas on mobile via Alpine mobileMenuOpen,
pinned at 16rem on lg), .app-topbar (fixed, blurred, 4rem), and
.app-subbar for in-page sticky bars (parks under the topbar). Content is
auto-offset via body:has(.app-sidebar) so reader.templ/error.templ (which
have no sidebar) are untouched.
- Header rebuilt as the sidebar: logo + vertical nav (activeClass), an
inline Appearance picker driven by ThemeOptions/WoodOptions, and an
inline account menu / sign-in (preserving the inline htmx login). The
search lives in the topbar so its dropdown still anchors correctly.
- Bolder primitives: .card -> rounded-2xl, cinematic .book-card-cover
hover overlay with a quick-action affordance, .brand-gradient hero
surface, .hero-backdrop (blurred cover) and .stat-card utilities.