feat: add Gemini connection test button in config panel

probarGemini() sends a minimal prompt to gemini-1.5-flash and reports
latency + trimmed response text, or the error message from the API.
Mirrors the existing Whisper test button pattern.

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

resources/views/livewire/chat/show-configuracion-chat.blade.php

@@ -82,6 +82,21 @@
                         class="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:ring-2 focus:ring-emerald-500 outline-none resize-none"
                         placeholder="Ej: Solo vendemos streaming. No ofrecemos juegos."></textarea>
                 </div>
+                <div>
+                    <button wire:click="probarGemini"
+                        class="flex items-center gap-2 px-4 py-2 bg-blue-600 hover:bg-blue-700 text-white text-sm font-semibold rounded-lg transition">
+                        <svg class="w-4 h-4" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor">
+                            <path stroke-linecap="round" stroke-linejoin="round" d="M9.813 15.904 9 18.75l-.813-2.846a4.5 4.5 0 0 0-3.09-3.09L2.25 12l2.846-.813a4.5 4.5 0 0 0 3.09-3.09L9 5.25l.813 2.846a4.5 4.5 0 0 0 3.09 3.09L15.75 12l-2.846.813a4.5 4.5 0 0 0-3.09 3.09Z" />
+                        </svg>
+                        <span wire:loading.remove wire:target="probarGemini">Probar conexión Gemini</span>
+                        <span wire:loading wire:target="probarGemini">Probando...</span>
+                    </button>
+                    @if($geminiResult)
+                        <p class="mt-2 text-sm {{ str_contains($geminiResult, '✅') ? 'text-emerald-600' : 'text-red-600' }}">
+                            {{ $geminiResult }}
+                        </p>
+                    @endif
+                </div>
             </div>
         </div>