refactor(open-banking): drop per-provider log-message hook

validationFailureLogMessage() was an abstract hook whose only job was to return a
cosmetically different warning string per provider ("Binance credential validation
failed", "Indexa Capital token validation failed", ...). It carried no functional
value and forced five one-line overrides.

Log a single structured message in the base with the provider enum value as
context, which is more useful for filtering than the free-text variants, and
remove the hook and its five overrides. Also restore the array-shape PHPDoc on
IndexaCapital's buildPendingAccounts() that the shared mixed signature dropped.

Only the warning-log text changes (now includes a "provider" key); the HTTP
responses are untouched. OpenBanking feature tests pass (304/304).

app/Http/Controllers/OpenBanking/BinanceController.php

@@ -41,11 +41,6 @@ class BinanceController extends CryptoPortfolioConnectController
         return null;
     }
 
-    protected function validationFailureLogMessage(): string
-    {
-        return 'Binance credential validation failed';
-    }
-
     protected function credentialErrorMessage(\Throwable $e): string
     {
         return 'Invalid API credentials or failed to connect to Binance.';

app/Http/Controllers/OpenBanking/BitpandaController.php

@@ -41,11 +41,6 @@ class BitpandaController extends CryptoPortfolioConnectController
         return null;
     }
 
-    protected function validationFailureLogMessage(): string
-    {
-        return 'Bitpanda credential validation failed';
-    }
-
     protected function credentialErrorMessage(\Throwable $e): string
     {
         return 'Invalid API key or failed to connect to Bitpanda.';

app/Http/Controllers/OpenBanking/CoinbaseController.php

@@ -41,11 +41,6 @@ class CoinbaseController extends CryptoPortfolioConnectController
         return null;
     }
 
-    protected function validationFailureLogMessage(): string
-    {
-        return 'Coinbase credential validation failed';
-    }
-
     protected function credentialErrorMessage(\Throwable $e): string
     {
         return 'Invalid API credentials or failed to connect to Coinbase.';

app/Http/Controllers/OpenBanking/IndexaCapitalController.php

@@ -46,11 +46,6 @@ class IndexaCapitalController extends OpenBankingConnectController
         return $client->getUser();
     }
 
-    protected function validationFailureLogMessage(): string
-    {
-        return 'Indexa Capital token validation failed';
-    }
-
     protected function credentialErrorMessage(\Throwable $e): string
     {
         return 'Invalid API token or failed to connect to Indexa Capital.';
@@ -58,6 +53,8 @@ class IndexaCapitalController extends OpenBankingConnectController
 
     /**
      * Build the pending accounts data in the same format as EnableBanking.
+     *
+     * @param  array{accounts?: array<int, array{account_number?: string, type?: string}>}  $providerData
      */
     protected function buildPendingAccounts(mixed $providerData, User $user): array
     {

app/Http/Controllers/OpenBanking/InteractiveBrokersController.php

@@ -48,11 +48,6 @@ class InteractiveBrokersController extends OpenBankingConnectController
         return $client->fetchStatement();
     }
 
-    protected function validationFailureLogMessage(): string
-    {
-        return 'Interactive Brokers connection validation failed';
-    }
-
     /**
      * Turn a Flex failure into a message the user can act on: bad credentials,
      * a busy/rate-limited service, or a statement that is still generating.

app/Http/Controllers/OpenBanking/OpenBankingConnectController.php

@@ -42,8 +42,6 @@ abstract class OpenBankingConnectController extends Controller
      */
     abstract protected function fetchProviderData(array $validated): mixed;
 
-    abstract protected function validationFailureLogMessage(): string;
-
     abstract protected function credentialErrorMessage(\Throwable $e): string;
 
     /**
@@ -77,7 +75,10 @@ abstract class OpenBankingConnectController extends Controller
         try {
             $providerData = $this->fetchProviderData($validated);
         } catch (\Throwable $e) {
-            Log::warning($this->validationFailureLogMessage(), ['error' => $e->getMessage()]);
+            Log::warning('OpenBanking credential validation failed', [
+                'provider' => $this->provider()->value,
+                'error' => $e->getMessage(),
+            ]);
 
             return response()->json([
                 'message' => $this->credentialErrorMessage($e),