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

components/chat-input.tsx

@@ -29,6 +29,7 @@ interface ChatInputProps {
     onFileChange?: (files: File[]) => void;
     showHistory?: boolean;
     onToggleHistory?: (show: boolean) => void;
+    sessionId?: string;
 }
 
 export function ChatInput({
@@ -41,6 +42,7 @@ export function ChatInput({
     onFileChange = () => {},
     showHistory = false,
     onToggleHistory = () => {},
+    sessionId,
 }: ChatInputProps) {
     const { diagramHistory, saveDiagramToFile } = useDiagram();
     const textareaRef = useRef<HTMLTextAreaElement>(null);
@@ -249,7 +251,7 @@ export function ChatInput({
                         <SaveDialog
                             open={showSaveDialog}
                             onOpenChange={setShowSaveDialog}
-                            onSave={saveDiagramToFile}
+                            onSave={(filename, format) => saveDiagramToFile(filename, format, sessionId)}
                             defaultFilename={`diagram-${new Date().toISOString().slice(0, 10)}`}
                         />