fix(core): align entropy code with bull sdk

Author: FrancisPouliot

lib/core/entropy/domain/usecases/mix_entropy_usecase.dart

@@ -4,8 +4,7 @@ import 'package:bb_mobile/core/entropy/data/services/entropy_pool.dart';
 
 /// Owns the touch-ceremony lifecycle exposed to onboarding.
 class MixEntropyUsecase {
-  const MixEntropyUsecase({required EntropyPool entropyPool})
-    : _entropyPool = entropyPool;
+  const MixEntropyUsecase({required this._entropyPool});
 
   static const requiredSampleCount = EntropyPool.requiredTouchSamples;
 

lib/core/seed/data/services/mnemonic_generator.dart

@@ -11,11 +11,7 @@ import 'package:bull_sdk/bdk.dart' as bdk;
 /// platform CSPRNG draw. BDK performs deterministic BIP39 encoding only; its
 /// internal random mnemonic constructor is never used here.
 class MnemonicGenerator {
-  MnemonicGenerator({
-    required EntropyPool entropyPool,
-    required OsRngSource osRngSource,
-  }) : _entropyPool = entropyPool,
-       _osRngSource = osRngSource;
+  MnemonicGenerator({required this._entropyPool, required this._osRngSource});
 
   final EntropyPool _entropyPool;
   final OsRngSource _osRngSource;

lib/features/onboarding/presentation/entropy_ceremony_cubit.dart

@@ -26,9 +26,8 @@ class EntropyCeremonyState {
 
 /// Serializes pointer samples and feeds them into the current pool ceremony.
 class EntropyCeremonyCubit extends Cubit<EntropyCeremonyState> {
-  EntropyCeremonyCubit({required MixEntropyUsecase mixEntropyUsecase})
-    : _mixEntropyUsecase = mixEntropyUsecase,
-      super(const EntropyCeremonyState());
+  EntropyCeremonyCubit({required this._mixEntropyUsecase})
+    : super(const EntropyCeremonyState());
 
   final MixEntropyUsecase _mixEntropyUsecase;
   final Stopwatch _stopwatch = Stopwatch();

test/core_test/seed/mnemonic_generator_test.dart

@@ -3,7 +3,7 @@ import 'dart:typed_data';
 import 'package:bb_mobile/core/entropy/data/services/entropy_pool.dart';
 import 'package:bb_mobile/core/entropy/data/services/sources/os_rng_source.dart';
 import 'package:bb_mobile/core/seed/data/services/mnemonic_generator.dart';
-import 'package:bdk_dart/bdk.dart' as bdk;
+import 'package:bull_sdk/bdk.dart' as bdk;
 import 'package:flutter_test/flutter_test.dart';
 
 Uint8List fixedOsDraw() => Uint8List.fromList(