Detector caching & Arch (v0.1.3)

[vhrabar]

This pull request adds official Arch Linux (AUR) packaging for SecureEye, updates the documentation to cover Arch installation and usage, introduces a detector backend cache to improve performance, and makes several minor improvements and bugfixes. The most important changes are grouped below.

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Arch Linux packaging and documentation:

• Added PKGBUILD, .SRCINFO, and secureeye-authd.install files for Arch Linux/AUR, splitting SecureEye into two packages: libpam-secureeye (PAM module) and secureeye-authd (daemon and Python runtime). These handle dependencies, installation, and service setup for both x86_64 and aarch64 architectures. [1] [2] [3]
• Updated README.md with Arch Linux installation instructions, package details, and PAM configuration steps specific to Arch. [1] [2] [3]

Detector backend performance and reliability:

• Implemented a thread-safe cache for detector backends in detector_factory.py, so each backend is built only once per configuration, improving performance and avoiding repeated initialization. [1] [2]
• The daemon (authd/main.py) now warms up (pre-builds and caches) the detector on startup, reducing first authentication latency and logging a warning if warmup fails.

Timeout and deadline handling:

• Increased the PAM module's client/daemon communication timeout margin for greater reliability, especially on slower systems.
• Exposed the response margin in the daemon as a constant for clarity and maintainability.

Other improvements:

• Updated badges in README.md to show Copr build status and removed obsolete workflow badges.
• Clarified and expanded warnings about running meson install alongside distribution packages to prevent system conflicts.

These changes together make SecureEye easier to install and use on Arch Linux, improve authentication performance, and enhance reliability and documentation.