feat: add LLM prediction providers with structured output support

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

config/services.php

@@ -50,6 +50,20 @@ return [
         'model' => env('ANTHROPIC_MODEL', 'claude-sonnet-4-6'),
     ],
 
+    'openai' => [
+        'api_key' => env('OPENAI_API_KEY'),
+        'model' => env('OPENAI_MODEL', 'gpt-4o-mini'),
+    ],
+
+    'gemini' => [
+        'api_key' => env('GEMINI_API_KEY'),
+        'model' => env('GEMINI_MODEL', 'gemini-2.0-flash'),
+    ],
+
+    'llm' => [
+        'provider' => env('LLM_PREDICTION_PROVIDER', 'anthropic'),
+    ],
+
     'fuelalert' => [
         'api_key' => env('FUELALERT_API_KEY'),
     ],