feat: link user feedback and diagram saves to chat traces in Langfuse

- Update log-feedback API to find existing chat trace by sessionId and attach score to it
- Update log-save API to create span on existing chat trace instead of standalone trace
- Add thumbs up/down feedback buttons on assistant messages
- Add message regeneration and edit functionality
- Add save dialog with format selection (drawio, png, svg)
- Pass sessionId through components for Langfuse linking

package.json

@@ -25,6 +25,7 @@
         "@opentelemetry/sdk-trace-node": "^2.2.0",
         "@radix-ui/react-dialog": "^1.1.6",
         "@radix-ui/react-scroll-area": "^1.2.3",
+        "@radix-ui/react-select": "^2.2.6",
         "@radix-ui/react-slot": "^1.1.2",
         "@radix-ui/react-tooltip": "^1.1.8",
         "@vercel/analytics": "^1.5.0",