updated LLM configurations and added support for new models

backend/example.env

@@ -12,6 +12,8 @@ SYNC_COOLDOWN_MINUTES=30
 
 # LLM model to use for summarization
 LLM_MODEL=qwen2:7b-instruct-q4_K_M
+LLM_MODEL=phi3:3.8b-mini-128k-instruct-q4_0
+LLM_MODEL=mistral-nemo:12b
 
 # Timeout in seconds for LLM requests
 LLM_TIMEOUT_SECONDS=180