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/widgets/create_menu.dart

@@ -0,0 +1,119 @@
+import 'package:file_picker/file_picker.dart';
+import 'package:flutter/material.dart';
+import 'package:lucide_icons_flutter/lucide_icons.dart';
+import 'package:provider/provider.dart';
+import '../providers/files_controller.dart';
+import '../services/share_intent_service.dart';
+import '../views/share_upload_view.dart';
+import 'noo/core/noo_button.dart';
+import 'noo/lists/noo_grouped_list.dart';
+import 'noo/lists/noo_settings_row.dart';
+import 'noo/overlays/noo_dialog.dart';
+import 'noo/overlays/noo_sheet.dart';
+import 'noo/overlays/noo_text_field.dart';
+
+/// The Files tab's "+"/FAB action: upload a file or create a folder into
+/// the current folder. Shared by `FilesView`'s own create button and
+/// `MainShellView`'s FAB (the Noo Design System project's FAB component),
+/// since both need to trigger the exact same flow.
+void showCreateMenu(BuildContext context) {
+  showNooSheet(
+    context,
+    children: [
+      NooGroupedList(
+        children: [
+          NooSettingsRow(
+            icon: LucideIcons.upload,
+            label: const Text('Upload file'),
+            onTap: () {
+              Navigator.pop(context);
+              _pickAndUploadFile(context);
+            },
+          ),
+          NooSettingsRow(
+            icon: LucideIcons.folder,
+            label: const Text('New folder'),
+            onTap: () {
+              Navigator.pop(context);
+              _showCreateFolderDialog(context);
+            },
+          ),
+        ],
+      ),
+    ],
+  );
+}
+
+void _showCreateFolderDialog(BuildContext context) {
+  final files = context.read<FilesController>();
+  final controller = TextEditingController();
+
+  Future<void> submit(BuildContext ctx) async {
+    final name = controller.text.trim();
+    if (name.isEmpty) return;
+    Navigator.pop(ctx);
+    final success = await files.createFolder(name);
+    if (ctx.mounted) {
+      ScaffoldMessenger.of(ctx).showSnackBar(
+        SnackBar(
+          content: Text(success ? 'Created folder $name' : 'Failed to create folder'),
+          behavior: SnackBarBehavior.floating,
+        ),
+      );
+    }
+  }
+
+  showNooDialog<void>(
+    context,
+    title: 'New folder',
+    children: [
+      NooTextField(
+        controller: controller,
+        placeholder: 'e.g. Finance',
+        autofocus: true,
+        onSurface: false,
+        onSubmitted: (_) => submit(context),
+      ),
+      Row(
+        mainAxisAlignment: MainAxisAlignment.end,
+        spacing: 10,
+        children: [
+          NooButton(
+            variant: NooButtonVariant.secondary,
+            onTap: () => Navigator.pop(context),
+            child: const Text('Cancel'),
+          ),
+          NooButton(
+            variant: NooButtonVariant.primary,
+            onTap: () => submit(context),
+            child: const Text('Create'),
+          ),
+        ],
+      ),
+    ],
+  );
+}
+
+// Mirrors `main.dart`'s `_handleSharedFiles` exactly, so picking a file via
+// "+"/the FAB lands on the same destination-picker screen and background
+// foreground-service upload as receiving one via Android's "Share to..."
+// sheet does, rather than a separate in-app-only upload path.
+Future<void> _pickAndUploadFile(BuildContext context) async {
+  final picked = await FilePicker.pickFiles();
+  if (picked.isEmpty) return;
+  final files = picked
+      .where((f) => f.path != null)
+      .map(
+        (f) => SharedFileRef(
+          uri: Uri.file(f.path!).toString(),
+          name: f.name,
+          size: f.lengthSync(),
+        ),
+      )
+      .toList();
+  if (files.isEmpty || !context.mounted) return;
+
+  Navigator.of(
+    context,
+  ).push(MaterialPageRoute(builder: (_) => ShareUploadView(files: files)));
+}