Enhance security and localization features across the application

- Added rehype-sanitize plugin to the markdown configuration for improved security against XSS attacks.
- Updated environment variables in the codebase to include new configurations for SMTP and monitoring.
- Implemented secure headers in server and Nginx configurations to bolster security.
- Refactored email handling to prevent spoofing by ensuring safe sender addresses.
- Improved localization by updating language persistence and button components for better user experience.
- Enhanced the uptime API and contact form with better error handling and logging practices.
- Updated dependencies in package.json and package-lock.json for better performance and security.

public/_headers

@@ -1,2 +1,12 @@
 /_astro/*
   Cache-Control: public, max-age=31536000, immutable
+
+/*
+  X-Content-Type-Options: nosniff
+  Referrer-Policy: strict-origin-when-cross-origin
+  Permissions-Policy: geolocation=(), camera=(), microphone=(), interest-cohort=()
+  Cross-Origin-Opener-Policy: same-origin
+  Cross-Origin-Embedder-Policy: require-corp
+  Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
+  # Content-Security-Policy starter (enable after auditing inline scripts)
+  # Content-Security-Policy: default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https://cdn.pixabay.com https://raw.githubusercontent.com; font-src 'self' data:; connect-src 'self'; frame-ancestors 'none'; base-uri 'self'; form-action 'self'