Add DeepSeek AI service integration

.env.example

@@ -1,18 +1,18 @@
 # API Keys Configuration
 # Copy this file to .env and fill in your actual keys
 
-# OpenAI API (for AI features)
-# Get from: https://platform.openai.com/api-keys
-OPENAI_API_KEY=your_openai_api_key_here
+# DeepSeek API (recommended - cost effective)
+# Get from: https://platform.deepseek.com/api_keys
+DEEPSEEK_API_KEY=sk_your_deepseek_api_key_here
 
-# Anthropic API (alternative AI provider)
+# OpenAI API (alternative)
+# Get from: https://platform.openai.com/api-keys
+OPENAI_API_KEY=sk_your_openai_api_key_here
+
+# Anthropic API (alternative)
 # Get from: https://console.anthropic.com/
 ANTHROPIC_API_KEY=your_anthropic_api_key_here
 
-# Google AI API (Gemini)
-# Get from: https://makersuite.google.com/app/apikey
-GOOGLE_AI_API_KEY=your_google_ai_api_key_here
-
 # Firebase Configuration
 # These will be in your Firebase console
 FIREBASE_API_KEY=your_firebase_api_key