feat: Implement CSRF protection and PostgreSQL support

- Added CSRF protection mechanism in the backend with utility functions for token management.
- Introduced a new CSRF route to fetch the active CSRF token for SPA bootstrap flows.
- Updated the auth routes to validate CSRF tokens on sensitive operations.
- Configured PostgreSQL as a database option in the environment settings and Docker Compose.
- Created a new SQLite configuration file for local development.
- Enhanced the API client to automatically attach CSRF tokens to requests.
- Updated various frontend components to utilize the new site origin utility for SEO purposes.
- Modified Nginx configuration to improve redirection and SEO headers.
- Added tests for CSRF token handling in the authentication routes.

frontend/index.html

@@ -5,6 +5,7 @@
     <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="description" content="Free online tools for PDF, image, video, and text processing. Merge, split, compress, convert, watermark, protect & more — instantly." />
+    <meta name="google-site-verification" content="tx9YptvPfrvb115PeFBWpYpRhw_4CYHQXzpLKNXXV20" />
     <meta name="keywords" content="PDF tools, merge PDF, split PDF, compress PDF, PDF to Word, image converter, free online tools, Arabic PDF tools" />
     <meta name="author" content="Dociva" />
     <meta name="robots" content="index, follow" />