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>

app/Http/Livewire/Chat/ShowConfiguracionChat.php

@@ -17,6 +17,7 @@ class ShowConfiguracionChat extends Component
     public string $mensaje_transferencia = '';
     public string $webhookResult         = '';
     public string $whisperResult         = '';
+    public string $geminiResult          = '';
 
     // ── Gemini IA ─────────────────────────────────────────────
     public string $gemini_api_key        = '';
@@ -86,6 +87,43 @@ class ShowConfiguracionChat extends Component
         $this->alert('success', 'Configuracion guardada correctamente.');
     }
 
+    public function probarGemini(): void
+    {
+        $key = trim($this->gemini_api_key ?: \App\Models\ChatConfig::get('gemini_api_key'));
+
+        if (! $key) {
+            $this->geminiResult = '⚠️ La API Key de Gemini está vacía.';
+            return;
+        }
+
+        $url = 'https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-flash:generateContent';
+
+        try {
+            $inicio   = microtime(true);
+            $response = Http::timeout(10)
+                ->withHeaders(['Content-Type' => 'application/json'])
+                ->post("{$url}?key={$key}", [
+                    'contents'         => [['parts' => [['text' => 'Responde solo "ok"']]]],
+                    'generationConfig' => ['maxOutputTokens' => 5, 'temperature' => 0],
+                ]);
+
+            $ms   = (int) ((microtime(true) - $inicio) * 1000);
+            $data = $response->json();
+
+            if (! $response->successful() || isset($data['error'])) {
+                $msg = $data['error']['message'] ?? ('HTTP ' . $response->status());
+                $this->geminiResult = "❌ Gemini respondió con error: {$msg}";
+                return;
+            }
+
+            $texto = $data['candidates'][0]['content']['parts'][0]['text'] ?? '(sin texto)';
+            $this->geminiResult = "✅ Gemini OK ({$ms}ms) — respuesta: \"{$texto}\"";
+
+        } catch (\Throwable $e) {
+            $this->geminiResult = '❌ No se pudo conectar con Gemini: ' . $e->getMessage();
+        }
+    }
+
     public function resetearWhisper(): void
     {
         $url   = trim($this->whisper_url   ?: ChatConfig::get('whisper_url'));