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.

nginx/nginx.prod.conf

@@ -0,0 +1,65 @@
+upstream backend {
+    server backend:5000;
+}
+
+server {
+    listen 80;
+    server_name _;
+    client_max_body_size 100M;
+
+    # Redirect HTTP to HTTPS
+    return 301 https://$host$request_uri;
+}
+
+server {
+    listen 443 ssl http2;
+    server_name _;
+    client_max_body_size 100M;
+
+    # SSL certificates (mount via certbot / Let's Encrypt)
+    ssl_certificate /etc/nginx/ssl/fullchain.pem;
+    ssl_certificate_key /etc/nginx/ssl/privkey.pem;
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_prefer_server_ciphers on;
+    ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256;
+
+    # Security headers
+    add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
+    add_header X-Frame-Options "SAMEORIGIN" always;
+    add_header X-Content-Type-Options "nosniff" always;
+    add_header X-XSS-Protection "1; mode=block" always;
+    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
+
+    # Gzip
+    gzip on;
+    gzip_types text/plain text/css application/json application/javascript text/xml application/xml text/javascript image/svg+xml;
+    gzip_min_length 1000;
+
+    # API requests → Flask
+    location /api/ {
+        proxy_pass http://backend;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+        proxy_read_timeout 300s;
+        proxy_send_timeout 300s;
+    }
+
+    # Frontend static files
+    location / {
+        root /usr/share/nginx/html;
+        try_files $uri $uri/ /index.html;
+
+        # Cache static assets
+        location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff2?)$ {
+            expires 1y;
+            add_header Cache-Control "public, immutable";
+        }
+    }
+
+    # Health check
+    location /health {
+        proxy_pass http://backend/api/health;
+    }
+}