Fix evaluation double-click submit: autosave was blocking the submit button

Root cause: submit button was disabled when autosaveMutation.isPending was true.
If the 3-second autosave timer fired while the user clicked Submit, the click
was silently swallowed. User had to wait for autosave to finish, then click again.

Fixes:
- Remove autosaveMutation.isPending from submit button disabled state
- Cancel pending autosave timer when submit starts (prevents race condition)
- Add isSubmittingRef guard to prevent autosave from firing during submit
- Reset submitting flag on validation failure or submit error

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

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

@@ -40,6 +40,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
   const isDirtyRef = useRef(false)
   const evaluationIdRef = useRef<string | null>(null)
   const isSubmittedRef = useRef(false)
+  const isSubmittingRef = useRef(false)
   const autosaveTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
   const [lastSavedAt, setLastSavedAt] = useState<Date | null>(null)
 
@@ -203,7 +204,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
 
   // Perform autosave
   const performAutosave = useCallback(async () => {
-    if (!isDirtyRef.current || isSubmittedRef.current) return
+    if (!isDirtyRef.current || isSubmittedRef.current || isSubmittingRef.current) return
     if (existingEvaluation?.status === 'SUBMITTED') return
 
     let evalId = evaluationIdRef.current
@@ -311,8 +312,16 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
   }
 
   const handleSubmit = async () => {
+    // Cancel any pending autosave to avoid race conditions
+    if (autosaveTimerRef.current) {
+      clearTimeout(autosaveTimerRef.current)
+      autosaveTimerRef.current = null
+    }
+    isSubmittingRef.current = true
+
     if (!myAssignment) {
       toast.error('Assignment not found')
+      isSubmittingRef.current = false
       return
     }
 
@@ -325,14 +334,17 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
         const val = criteriaValues[c.id]
         if (c.type === 'numeric' && (val === undefined || val === null)) {
           toast.error(`Please score "${c.label}"`)
+          isSubmittingRef.current = false
           return
         }
         if (c.type === 'boolean' && val === undefined) {
           toast.error(`Please answer "${c.label}"`)
+          isSubmittingRef.current = false
           return
         }
         if (c.type === 'text' && (!val || (typeof val === 'string' && !val.trim()))) {
           toast.error(`Please fill in "${c.label}"`)
+          isSubmittingRef.current = false
           return
         }
       }
@@ -342,6 +354,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
       const score = parseInt(globalScore, 10)
       if (isNaN(score) || score < 1 || score > 10) {
         toast.error('Please enter a valid score between 1 and 10')
+        isSubmittingRef.current = false
         return
       }
     }
@@ -349,6 +362,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
     if (scoringMode === 'binary') {
       if (!binaryDecision) {
         toast.error('Please select accept or reject')
+        isSubmittingRef.current = false
         return
       }
     }
@@ -356,6 +370,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
     if (requireFeedback) {
       if (!feedbackText.trim() || feedbackText.length < feedbackMinLength) {
         toast.error(`Please provide feedback (minimum ${feedbackMinLength} characters)`)
+        isSubmittingRef.current = false
         return
       }
     }
@@ -398,6 +413,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
       })
     } catch {
       // Error toast already handled by onError callback
+      isSubmittingRef.current = false
     }
   }
 
@@ -862,7 +878,7 @@ export default function JuryEvaluatePage({ params: paramsPromise }: PageProps) {
           </Button>
           <Button
             onClick={handleSubmit}
-            disabled={submitMutation.isPending || autosaveMutation.isPending || startMutation.isPending}
+            disabled={submitMutation.isPending || startMutation.isPending}
             className="bg-brand-blue hover:bg-brand-blue-light"
           >
             <Send className="mr-2 h-4 w-4" />