[vhrabar]

Closes #17

The release adds SecureEye app (secure-eye-gui): enroll face models with a live camera preview, test recognition, switch face login and edit the configuration. To make that possible, secureeye-authd became the single owner of the camera and the face models, with a management protocol, per-user access checks and login priority over the app. Recognition moved behind backend-agnostic interfaces with a versioned model store, in preparation for the ONNX pipeline (#33), which is not part of this release.

What's included

Pipeline interfaces and model store (#53; #34, #35)

• Detector / Recognizer / LivenessCheck interfaces, with dlib wrapped behind them, and a Pipeline that runs
  detect -> liveness -> recognize -> match.
• A versioned template store: every face model records the recognizer that made it, and models from different
  recognizers are never compared. A login with mismatched models says so (new PAM result code 16).
• secureEye re-enroll, and --json output for the CLI commands the app uses.

Daemon (#53, #54; #24)

• Protocol cleanup into one module, concurrent clients with read deadlines and a connection cap, and a camera arbiter
  that gives PAM logins priority over app sessions.
• Per-frame reports, enrollment and a recognition test as cancellable daemon-side sessions.
• Protocol v2 (docs/auth-protocol-v2.md): list, remove and clear models, enroll and test with live JPEG previews.
  Cancel and disconnect release the camera within about 200 ms; a login preempts a running session.
• Access: the socket is open to all users and each request is checked against the caller's SO_PEERCRED uid; face
  models belong to the secureeye user (tmpfiles.d), and root's CLI writes keep that ownership.

The app (#58; #30, #55)

• Face models page, enroll dialog and recognition test dialog, all through the daemon; a dashboard camera card that
  follows hotplug; tools/dev/gui-sandbox.sh to run the app against a development daemon.

Packaging (#60; #59)

• secure-eye-gui as its own package on Ubuntu, Fedora and Arch, under the app ID io.github.vhrabar.SecureEye, with
  desktop entry, icon and AppStream metainfo.