Security: Replace API keys with placeholders in .env.example

.env.example

@@ -32,9 +32,9 @@ OLLAMA__MODEL=llama3.2
 
 # --- LLM (Groq / Gemini — existing providers) ---
 LLM__PRIMARY_PROVIDER=groq
-LLM__GROQ_API_KEY=
+LLM__GROQ_API_KEY=your_groq_api_key_here
 LLM__GROQ_MODEL=llama-3.3-70b-versatile
-LLM__GEMINI_API_KEY=
+LLM__GEMINI_API_KEY=your_google_api_key_here
 LLM__GEMINI_MODEL=gemini-2.0-flash
 
 # --- Embeddings ---