4026f6dafa
Security: prevent double unlock() when PAM and fingerprint succeed simultaneously (ext-session-lock protocol error). Fix PAM callback returning PAM_AUTH_ERR instead of PAM_BUF_ERR on calloc OOM. Performance: replace CPU-side Gaussian blur (image crate) with GPU blur via GskBlurNode + GskRenderer::render_texture(). Eliminates 500ms-2s main-thread blocking on cold cache for 4K wallpapers. Remove image and dirs dependencies (~15 transitive crates). Make fingerprint stop() fire-and-forget async to avoid 6s UI block after successful auth.