feat(web): integrate Claude LLM streaming with markdown rendering

- Add Anthropic SDK with DeepSeek-compatible API config
- Streaming tool-use loop in WebSocket chat handler
- GitHub-style markdown rendering with markdown-it
- Tool status indicators and thinking states in chat UI
- Fix Tailwind content path and CSS border utility

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/client/tailwind.config.ts

@@ -1,7 +1,7 @@
 import type { Config } from 'tailwindcss';
 
 export default {
-  content: ['./client/src/**/*.{ts,tsx}'],
+  content: ['./src/**/*.{ts,tsx}'],
   darkMode: 'class',
   theme: {
     extend: {