Rebuild UI on the Noo design system

Replaces the Material 3 screens with the Noo design system: warm
neutrals, one violet accent, pill controls, Schibsted Grotesk/
Instrument Sans, Lucide icons, no gradients/shadows.

- New lib/widgets/noo/ component kit (core, lists, files, media, nav,
  overlays) plus lib/theme/design_tokens.dart for the color/type/space/
  radius/motion tokens.
- Rebuilt the app shell (top/bottom bars, drawer, desktop sidebar and
  toolbar), every tab (Files/Offline, Photos, Favorites, Recent,
  Activity, Trash, Shares), Settings, the lock and login screens, the
  media viewer, search, the details/share sheets, and the share-upload
  and move/copy destination pickers.
- Added a design canvas (linked from DESIGN_SYSTEM.md) covering the
  screens the spec didn't already describe, with matching Android and
  iOS chrome; wrote up the approved recipes into DESIGN_SYSTEM.md §4.
- Removed now-dead legacy widgets (media_grid_tile, swipeable_item,
  sync_status_badge, selectable_thumbnail) and updated
  architecture.md/styling.md/standards.md to describe the new
  structure and component/testing conventions.
- Added widget tests for the noo/ component kit.

This is a UI-only rework: no provider/model/service behavior changed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/views/login_webview_view.dart

@@ -1,7 +1,11 @@
 import 'package:flutter/material.dart';
+import 'package:lucide_icons_flutter/lucide_icons.dart';
 import 'package:provider/provider.dart';
 import 'package:webview_flutter/webview_flutter.dart';
 import '../providers/session_controller.dart';
+import '../theme/design_tokens.dart';
+import '../widgets/noo/nav/noo_top_bar.dart';
+import '../widgets/noo/noo_layout.dart';
 
 /// Every Login Flow v2 page - first login or an additional account -
 /// rendered in Flutter's own WebView rather than a Chrome Custom Tab or
@@ -63,6 +67,7 @@ class _LoginWebViewViewState extends State<LoginWebViewView> {
   @override
   Widget build(BuildContext context) {
     final session = context.watch<SessionController>();
+    final colors = context.nooColors;
 
     // The login flow finished (success or error) or was cancelled
     // elsewhere - close this screen automatically rather than leaving it
@@ -81,18 +86,24 @@ class _LoginWebViewViewState extends State<LoginWebViewView> {
         if (!didPop) _cancel();
       },
       child: Scaffold(
-        appBar: AppBar(
-          title: const Text('Sign in'),
-          leading: IconButton(
-            icon: const Icon(Icons.close_rounded),
+        backgroundColor: colors.bg,
+        appBar: NooTopBar(
+          style: NooLayout.navStyle(context),
+          title: 'Log in',
+          leading: NooTopBarButton(
+            icon: LucideIcons.x,
             tooltip: 'Cancel',
-            onPressed: _cancel,
+            onTap: _cancel,
           ),
         ),
         body: Stack(
           children: [
             WebViewWidget(controller: _controller),
-            if (_pageLoading) const LinearProgressIndicator(),
+            if (_pageLoading)
+              LinearProgressIndicator(
+                color: colors.accent,
+                backgroundColor: colors.surface3,
+              ),
           ],
         ),
       ),