feat(ui): refresh auth, entry, admin, and secondary pages

Apply the new design-system primitives across the remaining pages so the
whole app shares one visual language:

- Auth/entry: redesigned index, login, register (centered card layout,
  SVG icons, semantic tokens)
- Admin: sidebar nav with icons, cohesive admin dashboard/users/library/
  processing-issues/settings (tables use border-line + hover states;
  scan/websocket attributes preserved)
- Secondary: analytics (stat cards), devices, progress, conflicts, queue,
  profile + form/modal all migrated to .card/.btn/.input primitives and
  SVG action icons
- Docs + API explorer + setup wizard + collection/rules/modals +
  unlinked books + book-detail modals: consistent chrome, modal scrims
  use --surface-overlay, close buttons use icon-btn
- reader.templ and error.templ intentionally left unchanged

templates/profile_modal.templ

@@ -1,22 +1,21 @@
 package templates
 
 templ ProfileModal(user User) {
-	<div id="profile-modal" class="fixed inset-0 flex items-center justify-center z-50" x-data="profileModal" x-init="setupProfileModal()" style="background-color: rgba(0,0,0,0.5);">
-		<div class="rounded-lg shadow-xl max-w-4xl w-full mx-4 max-h-[90vh] overflow-y-auto" style="background-color: var(--bg-secondary);">
+	<div id="profile-modal" class="fixed inset-0 flex items-center justify-center z-50" x-data="profileModal" x-init="setupProfileModal()" style="background-color: var(--surface-overlay);">
+		<div class="card max-w-4xl w-full mx-4 max-h-[90vh] overflow-y-auto">
 			<!-- Modal Header -->
-			<div class="flex justify-between items-center p-6 border-b" style="border-color: var(--border);">
+			<div class="flex justify-between items-center p-6 border-b border-line">
 				<div>
-					<h2 class="text-2xl font-bold" style="color: var(--text-primary)">Edit User Profile</h2>
-					<p class="text-sm mt-1" style="color: var(--text-secondary);">
+					<h2 class="text-2xl font-bold tracking-tight text-content">Edit User Profile</h2>
+					<p class="text-sm mt-1 text-content-muted">
 						{ user.Username } ({ user.Email })
 					</p>
 				</div>
 				<button
 					@click="closeProfileModal()"
-					class="text-2xl"
-					style="color: var(--text-secondary);"
+					class="btn btn-ghost"
 				>
-					&times;
+					@Icon("close", "h-5 w-5")
 				</button>
 			</div>