fix: GeminiVisionService tries v1+v1beta, shows real API error in Telegram

- Rewrote extraerPago() to try v1 then v1beta for model compatibility
- Returns __error key with actual API message when both fail
- TelegramBotService shows that error in chat instead of generic message
- Also ensures model is read fresh from config (no hardcoded URL in constructor)

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

app/Services/TelegramBotService.php

@@ -187,6 +187,11 @@ class TelegramBotService
                 return;
             }
 
+            if (isset($datosPago['__error'])) {
+                $this->send($chatId, "⚠️ Error al analizar el comprobante:\n`" . $datosPago['__error'] . "`");
+                return;
+            }
+
             $resultado = app(PagoValidadorService::class)->validar($datosPago);
             $monto     = number_format($datosPago['valor'] ?? 0);
             $ref       = $datosPago['referencia'] ?? 'N/A';