fix: [BUG-004] import history refreshes after CSV import

Solution: Force remount ImportHistory via key prop
- Added importHistoryKey state (timestamp)
- Update key after import → triggers useEffect reload
- ImportHistory now updates immediately after import

Closes: BUG-004

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

frontend/src/pages/NutritionPage.jsx

@@ -743,6 +743,7 @@ export default function NutritionPage() {
   const [profile,    setProf]   = useState(null)
   const [loading,    setLoad]   = useState(true)
   const [hasData,    setHasData]= useState(false)
+  const [importHistoryKey, setImportHistoryKey] = useState(Date.now())  // BUG-004 fix
 
   const load = async () => {
     setLoad(true)
@@ -784,8 +785,8 @@ export default function NutritionPage() {
       {/* Import Panel + History */}
       {inputTab==='import' && (
         <>
-          <ImportPanel onImported={load}/>
-          <ImportHistory/>
+          <ImportPanel onImported={() => { load(); setImportHistoryKey(Date.now()) }}/>
+          <ImportHistory key={importHistoryKey}/>
         </>
       )}