feat(redpacket): 红包与游戏横幅全量实现 (#19~#24)

- #19 fix: SendRedEnvelopeUseCase 动态取 currencyType（workspaceId>0 取
  workspace.currency，修复 iOS 硬编码 PEA → 150001 错误）
- #20: RedEnvelopeBubble typ=8，四态（橙色领取/已领/过期/抢完）+ 领取按钮
- #21: ReceiveRedEnvelopeUseCase POST /app/api/wallet/rp/receive，
  typed JSON body（避免 code=30007），SnackBar 反馈
- #22: SendRedEnvelopeSheet BottomSheet，STANDARD_RP + LUCKY_RP，
  发送成功后构建 typ=8 content JSON 回调给 ChatPage
- #23: BannerViewModel Notifier，Group.topic 双格式解析（JSON object/string），
  FetchBannerUseCase + Timer 倒计时 + applyNewRound WS 接口
- #24: BannerView 游戏横幅条（状态/倒计时/上期结果），
  MiniAppFloatButton 悬浮按钮（hasGame 显示/隐藏，onTap TODO #25）

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/im_app/lib/features/chat/di/red_envelope_provider.dart

@@ -0,0 +1,22 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import 'package:im_app/app/di/network_provider.dart';
+import 'package:im_app/features/chat/usecases/send_red_envelope_usecase.dart';
+import 'package:im_app/features/chat/usecases/receive_red_envelope_usecase.dart';
+import 'package:im_app/features/chat/usecases/fetch_banner_usecase.dart';
+
+/// 发送红包 UseCase Provider
+final sendRedEnvelopeUseCaseProvider = Provider<SendRedEnvelopeUseCase>((ref) {
+  return SendRedEnvelopeUseCase(api: ref.read(networkSdkApiProvider));
+});
+
+/// 领取红包 UseCase Provider
+final receiveRedEnvelopeUseCaseProvider =
+    Provider<ReceiveRedEnvelopeUseCase>((ref) {
+  return ReceiveRedEnvelopeUseCase(api: ref.read(networkSdkApiProvider));
+});
+
+/// 游戏横幅 UseCase Provider
+final fetchBannerUseCaseProvider = Provider<FetchBannerUseCase>((ref) {
+  return FetchBannerUseCase(api: ref.read(networkSdkApiProvider));
+});