refactor(webui): dissolve core/css — co-locate each sheet with its owner

The generic core/css/{base,components,screens} buckets are gone; every shared
stylesheet now lives beside the subsystem that owns it:

  base/tokens.css, base/themes.css, components/aurora-background.css -> core/theme/
  base/style.css                                  -> core/theme/base.css (carve deferred)
  components/modal.css                            -> core/overlays/
  components/topbar.css, components/sidebar.css   -> core/topbar/
  components/forms.css, components/config.css     -> core/forms/   (config.css under forms)
  components/update-notifier.css                  -> core/update-notifier/
  screens/login.css                               -> core/boot/auth/
  screens/loading-screen.css                      -> core/loading/
  screens/setup-wizard.css                        -> core/setup/

href-only rewrites in index.html; the <link> line ORDER is unchanged, so the
cascade is preserved (no @import anywhere). All 13 /core css hrefs verified to
resolve. (The JS for overlays/topbar/forms/update-notifier/loading/setup/auth
co-locates in the next phase.)

Signed-off-by: librelad <librelad@digitalangels.vip>

containers/libreportal/frontend/index.html

@@ -11,33 +11,33 @@
 
   <!-- Styles -->
   <!-- Base token layer (theme-agnostic): --font-mono, --page-* identity hues -->
-  <link rel="stylesheet" href="/core/css/base/tokens.css">
+  <link rel="stylesheet" href="/core/theme/tokens.css">
-  <link rel="stylesheet" href="/core/css/base/themes.css">
+  <link rel="stylesheet" href="/core/theme/themes.css">
-  <link rel="stylesheet" href="/core/css/screens/loading-screen.css">
+  <link rel="stylesheet" href="/core/loading/loading-screen.css">
-  <link rel="stylesheet" href="/core/css/screens/setup-wizard.css">
+  <link rel="stylesheet" href="/core/setup/setup-wizard.css">
-  <link rel="stylesheet" href="/core/css/base/style.css">
+  <link rel="stylesheet" href="/core/theme/base.css">
   <link rel="stylesheet" href="/components/admin/config/css/ip-whitelist.css">
   <link rel="stylesheet" href="/components/apps/port-manager/css/port-manager.css">
   <link rel="stylesheet" href="/components/backup/core/css/backup.css">
   <link rel="stylesheet" href="/components/admin/ssh/css/ssh.css">
   <link rel="stylesheet" href="/components/admin/core/css/admin.css">
   <link rel="stylesheet" href="/components/apps/services/css/services.css">
-  <link rel="stylesheet" href="/core/css/components/modal.css">
+  <link rel="stylesheet" href="/core/overlays/modal.css">
   <link rel="stylesheet" href="/components/apps/tools/css/tools.css">
   <link rel="stylesheet" href="/components/apps/routing/css/routing.css">
-  <link rel="stylesheet" href="/core/css/screens/login.css">
+  <link rel="stylesheet" href="/core/boot/auth/login.css">
-  <link rel="stylesheet" href="/core/css/components/aurora-background.css">
+  <link rel="stylesheet" href="/core/theme/aurora-background.css">
-  <link rel="stylesheet" href="/core/css/components/topbar.css">
+  <link rel="stylesheet" href="/core/topbar/topbar.css">
-  <link rel="stylesheet" href="/core/css/components/sidebar.css">
+  <link rel="stylesheet" href="/core/topbar/sidebar.css">
   <link rel="stylesheet" href="/components/apps/core/css/apps-layout.css">
   <link rel="stylesheet" href="/components/apps/core/css/apps.css">
-  <link rel="stylesheet" href="/core/css/components/forms.css">
+  <link rel="stylesheet" href="/core/forms/forms.css">
-  <link rel="stylesheet" href="/core/css/components/config.css">
+  <link rel="stylesheet" href="/core/forms/config.css">
   <link rel="stylesheet" href="/components/apps/core/css/service-buttons.css">
   <link rel="stylesheet" href="/components/dashboard/css/dashboard.css">
   <link rel="stylesheet" href="/components/tasks/css/tasks.css">
   <link rel="stylesheet" href="/components/updater/css/updater.css">
-  <link rel="stylesheet" href="/core/css/components/update-notifier.css">
+  <link rel="stylesheet" href="/core/update-notifier/update-notifier.css">
   <script>
     // Inline data-theme bootstrap — runs before any rendering so the right
     // palette tokens resolve on first paint. Synchronously injects a