feat(client): add the Nostalgia appearance style

Add a Style setting beside mode, accent, radius and background. Nostalgia restyles the app through
tokens only (neutral surface palettes, system type, flat shell, top glow) and pins background,
opacity and brightness. Add a top glow reach slider for both styles. Tidy the theme layer first:
charts read live tokens, bare `rounded` follows the radius scale, one shared sign-in toolbar.
Also carries the settings page header redesign.

client/public/theme-init.js

@@ -2,19 +2,42 @@
   function readStoredValue(key, fallback) {
     var stored = localStorage.getItem(key)
     if (stored === null) return fallback
+    var value = stored
     try {
-      return JSON.parse(stored)
+      value = JSON.parse(stored)
     } catch {
-      return stored
+      value = stored
     }
+    return typeof value === 'string' ? value : fallback
   }
 
+  // Mirrors STANDALONE_ROUTE_PREFIXES in src/lib/theme-styles.ts; theme-init.spec.ts keeps them equal.
+  var STANDALONE_ROUTE_PREFIXES = ['/read/', '/login', '/register', '/setup', '/forgot-password', '/reset-password', '/oauth2-callback', '/magic']
+
+  function isAppShellPath(path) {
+    for (var i = 0; i < STANDALONE_ROUTE_PREFIXES.length; i++) {
+      var prefix = STANDALONE_ROUTE_PREFIXES[i]
+      if (path === prefix || path.indexOf(prefix.charAt(prefix.length - 1) === '/' ? prefix : prefix + '/') === 0) return false
+    }
+    return true
+  }
+
+  var root = document.documentElement
   var theme = readStoredValue('theme', 'system')
-  var accent = readStoredValue('accent', 'neutral')
+  var accent = readStoredValue('accent', 'blue')
   var radius = readStoredValue('radius', 'default')
+  var style = readStoredValue('style', 'bookorbit')
+  var surfacePalette = readStoredValue('surfacePalette', 'steel')
+  var rawReach = localStorage.getItem('glowReach')
+  var storedReach = rawReach === null ? 80 : Number(rawReach)
+  var glowReach = isFinite(storedReach) ? Math.min(200, Math.max(0, storedReach)) : 80
   var systemDark = typeof window.matchMedia === 'function' && window.matchMedia('(prefers-color-scheme: dark)').matches
   var isDark = theme === 'dark' || (theme !== 'light' && systemDark)
-  if (isDark) document.documentElement.classList.add('dark')
-  if (accent !== 'neutral') document.documentElement.classList.add('accent-' + accent)
-  if (radius !== 'default') document.documentElement.classList.add('radius-' + radius)
+  if (isDark) root.classList.add('dark')
+  root.classList.add('accent-' + accent)
+  if (radius !== 'default') root.classList.add('radius-' + radius)
+  root.setAttribute('data-style', isAppShellPath(window.location.pathname) ? style : 'bookorbit')
+  root.setAttribute('data-surface', surfacePalette)
+  root.style.setProperty('--glow-reach', String(glowReach / 100))
+  root.setAttribute('data-glow', glowReach > 0 ? 'on' : 'off')
 })()