feat: Initialize frontend with React, Vite, and Tailwind CSS

- Set up main entry point for React application.
- Create About, Home, NotFound, Privacy, and Terms pages with SEO support.
- Implement API service for file uploads and task management.
- Add global styles using Tailwind CSS.
- Create utility functions for SEO and text processing.
- Configure Vite for development and production builds.
- Set up Nginx configuration for serving frontend and backend.
- Add scripts for cleanup of expired files and sitemap generation.
- Implement deployment script for production environment.

frontend/src/hooks/useTaskPolling.ts

@@ -0,0 +1,87 @@
+import { useState, useEffect, useCallback, useRef } from 'react';
+import { getTaskStatus, type TaskStatus, type TaskResult } from '@/services/api';
+
+interface UseTaskPollingOptions {
+  taskId: string | null;
+  intervalMs?: number;
+  onComplete?: (result: TaskResult) => void;
+  onError?: (error: string) => void;
+}
+
+interface UseTaskPollingReturn {
+  status: TaskStatus | null;
+  isPolling: boolean;
+  result: TaskResult | null;
+  error: string | null;
+  stopPolling: () => void;
+}
+
+export function useTaskPolling({
+  taskId,
+  intervalMs = 1500,
+  onComplete,
+  onError,
+}: UseTaskPollingOptions): UseTaskPollingReturn {
+  const [status, setStatus] = useState<TaskStatus | null>(null);
+  const [isPolling, setIsPolling] = useState(false);
+  const [result, setResult] = useState<TaskResult | null>(null);
+  const [error, setError] = useState<string | null>(null);
+  const intervalRef = useRef<ReturnType<typeof setInterval> | null>(null);
+
+  const stopPolling = useCallback(() => {
+    if (intervalRef.current) {
+      clearInterval(intervalRef.current);
+      intervalRef.current = null;
+    }
+    setIsPolling(false);
+  }, []);
+
+  useEffect(() => {
+    if (!taskId) return;
+
+    setIsPolling(true);
+    setResult(null);
+    setError(null);
+
+    const poll = async () => {
+      try {
+        const taskStatus = await getTaskStatus(taskId);
+        setStatus(taskStatus);
+
+        if (taskStatus.state === 'SUCCESS') {
+          stopPolling();
+          const taskResult = taskStatus.result;
+
+          if (taskResult?.status === 'completed') {
+            setResult(taskResult);
+            onComplete?.(taskResult);
+          } else {
+            const errMsg = taskResult?.error || 'Processing failed.';
+            setError(errMsg);
+            onError?.(errMsg);
+          }
+        } else if (taskStatus.state === 'FAILURE') {
+          stopPolling();
+          const errMsg = taskStatus.error || 'Task failed.';
+          setError(errMsg);
+          onError?.(errMsg);
+        }
+      } catch (err) {
+        stopPolling();
+        const errMsg = err instanceof Error ? err.message : 'Polling failed.';
+        setError(errMsg);
+        onError?.(errMsg);
+      }
+    };
+
+    // Poll immediately, then set interval
+    poll();
+    intervalRef.current = setInterval(poll, intervalMs);
+
+    return () => {
+      stopPolling();
+    };
+  }, [taskId, intervalMs]); // eslint-disable-line react-hooks/exhaustive-deps
+
+  return { status, isPolling, result, error, stopPolling };
+}