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>

test_driver/integration_test.dart

@@ -0,0 +1,33 @@
+// Host-side driver for integration_test/store_screenshots_test.dart (run via
+// tool/screenshots.sh). Each time the test asks for a screenshot this saves
+// a PNG named after it into $SCREENSHOT_DIR.
+//
+// These bytes are the Flutter surface only (no OS status bar) - an earlier
+// version of this file tried to re-capture the screen with `adb exec-out
+// screencap` for a "real" screenshot including it, but on Android,
+// `onScreenshot` only fires once the whole test has finished (see
+// `IntegrationTestWidgetsFlutterBinding`/`integrationDriver`'s source: the
+// native platform channel hands screenshot bytes straight to `reportData`
+// with no round trip to the driver, and the driver's first `requestData`
+// call blocks until every `testWidgets` body in the file has returned) - so
+// every `adb screencap` call was capturing the same final frame, regardless
+// of which named screenshot it was meant to be. Saving these bytes directly
+// is what actually gives each name its own distinct image.
+import 'dart:io';
+
+import 'package:integration_test/integration_test_driver_extended.dart';
+
+Future<void> main() async {
+  final outDir = Directory(
+    Platform.environment['SCREENSHOT_DIR'] ?? 'store_listing/screenshots',
+  )..createSync(recursive: true);
+
+  await integrationDriver(
+    onScreenshot:
+        (String name, List<int> bytes, [Map<String, Object?>? args]) async {
+          File('${outDir.path}/$name.png').writeAsBytesSync(bytes);
+          stdout.writeln('saved $name.png');
+          return true;
+        },
+  );
+}