CW-1069-implement-deuro-dapp-support (#2304)

* feat: started dEuro Savings integration

* fix: merge conflict regarding theming

* feat: Add dEuro Savings Screen

* feat: Change DEuro Savings UI

* feat: Complete DEuro Savings integration with UI enhancements and transaction support

* style: remove forgotten print statements

* feat: localize dEuro subtitle

* feat: add approval flow and priority handling to DEuro Savings integration

- Introduced approval flow for DEuro Savings to enable token approvals.
- Added priority handling for deposit and withdrawal operations.
- Updated UI to support approval state and interactions.
- Localized new strings for multiple languages.
- Enhanced transaction handling with separate approval and commit actions.

* feat: add support for ERC20 token approval transactions

- Introduced `signApprovalTransaction` and `createApprovalTransaction` methods.
- Added handling for infinite approvals.
- Implemented encoding for approval transaction data.
- Enhanced transaction creation flow with approval-specific functionality.

* Update UI

* feat: enhance DEuro Savings logic and UI with computed property and fix gradient background

* feat: localize transaction confirmation content for DEuro Savings

* feat: enable interest collection for DEuro Savings with localized support

* fix reformatting [skip ci]

---------

Co-authored-by: tuxsudo <tuxsudo@tux.pizza>
Co-authored-by: OmarHatem <omarh.ismail1@gmail.com>

cw_evm/lib/evm_chain_client.dart

@@ -76,7 +76,7 @@ abstract class EVMChainClient {
   Future<int> getGasUnitPrice() async {
     try {
       final gasPrice = await _client!.getGasPrice();
-    
+
       return gasPrice.getInWei.toInt();
     } catch (_) {
       return 0;
@@ -101,6 +101,7 @@ abstract class EVMChainClient {
     String? contractAddress,
     EtherAmount? gasPrice,
     EtherAmount? maxFeePerGas,
+    Uint8List? data,
   }) async {
     try {
       if (contractAddress == null) {
@@ -124,7 +125,7 @@ abstract class EVMChainClient {
         final gasEstimate = await _client!.estimateGas(
           sender: senderAddress,
           to: EthereumAddress.fromHex(contractAddress),
-          data: transfer.encodeCall([
+          data: data ?? transfer.encodeCall([
             toAddress,
             value.getInWei,
           ]),
@@ -137,6 +138,21 @@ abstract class EVMChainClient {
     }
   }
 
+  Uint8List getEncodedDataForApprovalTransaction({
+    required EthereumAddress toAddress,
+    required EtherAmount value,
+    required EthereumAddress contractAddress,
+  }) {
+    final contract = DeployedContract(ethereumContractAbi, contractAddress);
+
+    final approve = contract.function('approve');
+
+    return approve.encodeCall([
+      toAddress,
+      value.getInWei,
+    ]);
+  }
+
   Future<PendingEVMChainTransaction> signTransaction({
     required Credentials privateKey,
     required String toAddress,
@@ -198,6 +214,50 @@ abstract class EVMChainClient {
     );
   }
 
+  Future<PendingEVMChainTransaction> signApprovalTransaction({
+    required Credentials privateKey,
+    required String spender,
+    required BigInt amount,
+    required BigInt gasFee,
+    required int estimatedGasUnits,
+    required int maxFeePerGas,
+    required EVMChainTransactionPriority priority,
+    required int exponent,
+    required String contractAddress,
+  }) async {
+
+    final Transaction transaction = createTransaction(
+      from: privateKey.address,
+      to: EthereumAddress.fromHex(contractAddress),
+      maxPriorityFeePerGas: EtherAmount.fromInt(EtherUnit.gwei, priority.tip),
+      amount: EtherAmount.zero(),
+      maxGas: estimatedGasUnits,
+      maxFeePerGas: EtherAmount.fromInt(EtherUnit.wei, maxFeePerGas),
+    );
+
+    final erc20 = ERC20(
+      client: _client!,
+      address: EthereumAddress.fromHex(contractAddress),
+      chainId: chainId,
+    );
+
+    final signedTransaction = await erc20.approve(
+      EthereumAddress.fromHex(spender),
+      amount,
+      credentials: privateKey,
+      transaction: transaction,
+    );
+
+    return PendingEVMChainTransaction(
+      signedTransaction: prepareSignedTransactionForSending(signedTransaction),
+      amount: amount.toString(),
+      fee: gasFee,
+      sendTransaction: () => sendTransaction(signedTransaction),
+      exponent: exponent,
+      isInfiniteApproval: amount.toRadixString(16) == 'ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
+    );
+  }
+
   Transaction createTransaction({
     required EthereumAddress from,
     required EthereumAddress to,