Fix race condition: deduplicate startMutation calls between autosave and submit

Use a shared startPromiseRef so autosave and handleSubmit reuse the same
in-flight "create evaluation" promise instead of firing duplicate requests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/(jury)/jury/competitions/[roundId]/projects/[projectId]/evaluate/page.tsx

@@ -42,6 +42,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
   const isSubmittedRef = useRef(false)
   const isSubmittingRef = useRef(false)
   const [isSubmitting, setIsSubmitting] = useState(false)
+  const startPromiseRef = useRef<Promise<{ id: string }> | null>(null)
   const autosaveTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
   const [lastSavedAt, setLastSavedAt] = useState<Date | null>(null)
 
@@ -211,11 +212,17 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
     let evalId = evaluationIdRef.current
     if (!evalId && myAssignment) {
       try {
-        const newEval = await startMutation.mutateAsync({ assignmentId: myAssignment.id })
+        // Reuse in-flight start promise to avoid duplicate creation
+        if (!startPromiseRef.current) {
+          startPromiseRef.current = startMutation.mutateAsync({ assignmentId: myAssignment.id })
+        }
+        const newEval = await startPromiseRef.current
         evalId = newEval.id
         evaluationIdRef.current = evalId
       } catch {
         return
+      } finally {
+        startPromiseRef.current = null
       }
     }
     if (!evalId) return
@@ -297,7 +304,11 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
 
     let evaluationId = evaluationIdRef.current
     if (!evaluationId) {
-      const newEval = await startMutation.mutateAsync({ assignmentId: myAssignment.id })
+      if (!startPromiseRef.current) {
+        startPromiseRef.current = startMutation.mutateAsync({ assignmentId: myAssignment.id })
+      }
+      const newEval = await startPromiseRef.current
+      startPromiseRef.current = null
       evaluationId = newEval.id
       evaluationIdRef.current = evaluationId
     }
@@ -384,9 +395,14 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
       }
     }
 
+    // Reuse in-flight start promise to avoid duplicate creation (e.g. if autosave is mid-flight)
     let evaluationId = evaluationIdRef.current
     if (!evaluationId) {
-      const newEval = await startMutation.mutateAsync({ assignmentId: myAssignment.id })
+      if (!startPromiseRef.current) {
+        startPromiseRef.current = startMutation.mutateAsync({ assignmentId: myAssignment.id })
+      }
+      const newEval = await startPromiseRef.current
+      startPromiseRef.current = null
       evaluationId = newEval.id
       evaluationIdRef.current = evaluationId
     }