Update default model to mistral-large-2411 for improved agentic workflows

- Change default from mistral-small-latest to mistral-large-2411
- mistral-large-2411 is Mistral's flagship model (123B params)
- Optimized for complex agentic workflows with precise instruction following
- Supports 128k context window with robust function-calling and JSON outputs
- Better suited for multi-agent collaborative document editing

backend/src/services/mistralClient.js

@@ -52,7 +52,7 @@ async function callMistralAPI(messages, options = {}) {
       'Authorization': `Bearer ${MISTRAL_API_KEY}`
     },
     body: JSON.stringify({
-      model: options.model || 'mistral-small-latest',
+      model: options.model || 'mistral-large-2411',
       messages,
       temperature: options.temperature || 0.7,
       max_tokens: maxTokens || 2048,