feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/shared/widgets/buzz_loading_indicator.dart

@@ -0,0 +1,99 @@
+import 'dart:math' show pi;
+
+import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+
+import '../l10n/l10n.dart';
+import '../theme/theme.dart';
+
+/// The shared mobile loading indicator, matching the desktop arc spinner.
+class BuzzLoadingIndicator extends HookConsumerWidget {
+  /// The spinner diameter.
+  final double size;
+
+  /// An optional spinner color. Defaults to the active accent color.
+  final Color? color;
+
+  /// The accessibility announcement for this loading state.
+  final String? semanticLabel;
+
+  /// Creates a looping arc loading indicator.
+  const BuzzLoadingIndicator({
+    this.size = 40,
+    this.color,
+    this.semanticLabel,
+    super.key,
+  });
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final reducedMotion = MediaQuery.disableAnimationsOf(context);
+    final animation = useAnimationController(
+      duration: const Duration(milliseconds: 500),
+    );
+
+    useEffect(() {
+      if (reducedMotion) {
+        animation
+          ..stop()
+          ..value = 0;
+      } else {
+        animation.repeat();
+      }
+      return animation.stop;
+    }, [animation, reducedMotion]);
+
+    final spinnerColor = color ?? context.colors.primary;
+    final strokeWidth = (size / 6).clamp(2.0, 4.0);
+
+    return Semantics(
+      liveRegion: true,
+      label: semanticLabel ?? context.l10n.loading,
+      child: ExcludeSemantics(
+        child: RotationTransition(
+          key: const ValueKey('buzz-loading-indicator-spinner'),
+          turns: animation,
+          child: CustomPaint(
+            size: Size.square(size),
+            painter: _ArcSpinnerPainter(
+              color: spinnerColor,
+              strokeWidth: strokeWidth,
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class _ArcSpinnerPainter extends CustomPainter {
+  final Color color;
+  final double strokeWidth;
+
+  const _ArcSpinnerPainter({required this.color, required this.strokeWidth});
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    final center = size.center(Offset.zero);
+    final radius = (size.shortestSide - strokeWidth) / 2;
+    final bounds = Rect.fromCircle(center: center, radius: radius);
+    final trackPaint = Paint()
+      ..color = color.withValues(alpha: color.a * 0.1)
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = strokeWidth;
+    final arcPaint = Paint()
+      ..color = color
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = strokeWidth;
+
+    canvas
+      ..drawCircle(center, radius, trackPaint)
+      ..drawArc(bounds, -pi / 2, pi / 2, false, arcPaint);
+  }
+
+  @override
+  bool shouldRepaint(_ArcSpinnerPainter oldDelegate) {
+    return color != oldDelegate.color || strokeWidth != oldDelegate.strokeWidth;
+  }
+}