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.

backend/app/routes/health.py

@@ -0,0 +1,14 @@
+"""Health check endpoint."""
+from flask import Blueprint, jsonify
+
+health_bp = Blueprint("health", __name__)
+
+
+@health_bp.route("/health", methods=["GET"])
+def health_check():
+    """Simple health check — returns 200 if the service is running."""
+    return jsonify({
+        "status": "healthy",
+        "service": "SaaS-PDF API",
+        "version": "1.0.0",
+    })