feat: add anthropic API proxy route to Caddyfile and revert to npm install in Dockerfile

Caddyfile

@@ -23,6 +23,13 @@
     }
     header @html Cache-Control "public, max-age=0, must-revalidate"
 
+    handle /api/anthropic/* {
+        uri strip_prefix /api/anthropic
+        reverse_proxy https://api.anthropic.com {
+            header_up Host api.anthropic.com
+        }
+    }
+
     try_files {path} /index.html
 
     handle_errors {