Add security status display for Secure LSL streams

[neuromechanist]

Summary

This PR adds support for displaying security status of LSL streams when using Secure LSL (sccn/secureLSL).

• Display lock icon and fingerprint for encrypted streams
• Show security mismatch detection with informative error dialogs
• Add version API info to About dialog

Dependencies

This PR requires the secure liblsl library from sccn/secureLSL (currently private, pending review).

Documentation: https://secure-lsl.pages.dev

Note

This is a draft PR. The secureLSL repository is not yet public; this PR is submitted for early review and discussion alongside the main secureLSL proposal for liblsl v2.