Rework app bar, notes layout, Settings/Admin/login restyle

App bar: brand, Studies / Read Bible / Reading Plans, and one account menu
(theme, Settings, Admin, Log out). Study stage: notes get their own box above
the resources in the right column. Settings, Admin and the login page use the
reader themes; add a theme-aware danger colour.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/components/reader/ReaderText.jsx

@@ -48,7 +48,7 @@ export default function ReaderText({
       </header>
 
       {loading && <p className="text-center font-sans text-sm text-[var(--r-sub)]">Loading…</p>}
-      {error && <p className="text-center font-sans text-sm text-red-600">{error}</p>}
+      {error && <p className="text-center font-sans text-sm text-[var(--r-danger,#b42318)]">{error}</p>}
 
       {!loading && !error && (
         <div