feat(web): add i18n locale routes and language switcher component

Add locale-prefixed routes for admin, auth, dashboard, and public pages.
Add error, loading, and not-found pages for locale context. Add language
switcher UI component for Vietnamese/English toggle.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/app/[locale]/(dashboard)/dashboard/valuation/page.tsx

@@ -0,0 +1,74 @@
+'use client';
+
+import { useState } from 'react';
+import { ValuationForm } from '@/components/valuation/valuation-form';
+import { ValuationHistory } from '@/components/valuation/valuation-history';
+import { ValuationResults } from '@/components/valuation/valuation-results';
+import {
+  useValuationPredict,
+  useValuationHistory,
+  useValuationDetail,
+} from '@/lib/hooks/use-valuation';
+import type { ValuationRequest, ValuationResult } from '@/lib/valuation-api';
+
+export default function ValuationPage() {
+  const [historyPage, setHistoryPage] = useState(1);
+  const [selectedId, setSelectedId] = useState<string | null>(null);
+
+  const predictMutation = useValuationPredict();
+  const { data: historyData, isLoading: historyLoading } = useValuationHistory(historyPage);
+  const { data: selectedResult } = useValuationDetail(selectedId ?? '');
+
+  const currentResult: ValuationResult | undefined =
+    predictMutation.data ?? selectedResult;
+
+  const handleSubmit = (data: ValuationRequest) => {
+    setSelectedId(null);
+    predictMutation.mutate(data);
+  };
+
+  const handleSelectHistory = (id: string) => {
+    setSelectedId(id);
+  };
+
+  return (
+    <div className="space-y-8">
+      <div>
+        <h1 className="text-3xl font-bold">Dinh gia AI</h1>
+        <p className="mt-2 text-muted-foreground">
+          Su dung AI de uoc tinh gia tri bat dong san dua tren du lieu thi truong
+        </p>
+      </div>
+
+      <div className="grid gap-6 lg:grid-cols-3">
+        {/* Form + Results */}
+        <div className="space-y-6 lg:col-span-2">
+          <ValuationForm
+            onSubmit={handleSubmit}
+            isLoading={predictMutation.isPending}
+          />
+
+          {predictMutation.isError && (
+            <div className="rounded-lg border border-destructive/50 bg-destructive/10 p-4 text-sm text-destructive">
+              Khong the dinh gia. Vui long thu lai sau.
+            </div>
+          )}
+
+          {currentResult && <ValuationResults result={currentResult} />}
+        </div>
+
+        {/* History sidebar */}
+        <div>
+          <ValuationHistory
+            items={historyData?.data ?? []}
+            total={historyData?.total ?? 0}
+            page={historyPage}
+            onPageChange={setHistoryPage}
+            onSelect={handleSelectHistory}
+            isLoading={historyLoading}
+          />
+        </div>
+      </div>
+    </div>
+  );
+}