Show login UI on all monitors for compositor-agnostic focus

Wayland does not expose absolute pointer coordinates to clients,
so we cannot reliably detect which monitor has focus. Instead,
show the full lockscreen UI on every monitor — the compositor
assigns keyboard focus to the surface under the pointer via
ext-session-lock-v1.

Share a single FingerprintListener across all windows to avoid
multiple device claims. Also add makepkg build artifacts to
gitignore.

.gitignore

@@ -5,3 +5,9 @@ __pycache__/
 dist/
 build/
 .pytest_cache/
+
+# makepkg build artifacts
+pkg/src/
+pkg/pkg/
+pkg/moonlock/
+pkg/*.pkg.tar.*