Improve security and privacy with strict meta tags

This commit introduces two meta tags to strengthen the application's
security posture and enhance user privacy, following best practices and
OWASP recommendations.

- Add Content-Security-Policy (CSP) to strictly to strictly control
  which resources the application is allowed, mitigating the risk of
  code injection attacks such as Cross-Site Scripting (XSS).
- Add `referrer` meta tag to prevent the users' browser from sending the
  page's address, or referrer, when navigating to another site, thereby
  enhancing user privacy.

docs/desktop-vs-web-features.md

@@ -35,7 +35,7 @@ The desktop version ensures secure delivery through cryptographic signatures and
 
 > **Note for macOS users:** On macOS, the desktop version's auto-update process involves manual steps due to Apple's code signing costs.
 > Users get notified about updates but might need to complete the installation manually.
-> Your [support through donations](https://github.com/sponsors/undergroundwires) can help improve this process ❤️.
+> Consider [donating](https://github.com/sponsors/undergroundwires) to help improve this process ❤️.
 
 ### Logging