feat(app): 完成 P0 钱包解锁、下载落盘与手机号登录

lib/core/widgets/download_action.dart

@@ -20,10 +20,16 @@ Future<void> requestEpisodeDownload(
   if (!await ensureSignedIn(context)) return;
   if (!context.mounted) return;
   unawaited(context.read<Haptics>().lightImpact());
-  final result = await context.read<DownloadController>().grant(episodeId);
+  final downloads = context.read<DownloadController>();
+  final result = await downloads.grant(episodeId);
   if (!context.mounted) return;
   final l10n = AppLocalizations.of(context)!;
   final hasBackendMessage = result.message?.trim().isNotEmpty ?? false;
+  if (result.ok) {
+    unawaited(
+      downloads.startDownload(episodeId, license: result.license),
+    );
+  }
   final message = result.ok
       ? l10n.downloadGranted
       : hasBackendMessage