Rewrite moonlock from Python to Rust (v0.4.0)

Complete rewrite of the Wayland lockscreen from Python/PyGObject to
Rust/gtk4-rs for memory safety in security-critical PAM code and
consistency with the moonset/moongreet Rust ecosystem.

Modules: main, lockscreen, auth (PAM FFI), fingerprint (fprintd D-Bus),
config, i18n, users, power. 37 unit tests.

Security: PAM conversation callback with Zeroizing password, panic hook
that never unlocks, root check, ext-session-lock-v1 compositor policy,
absolute loginctl path, avatar symlink rejection.

README.md

@@ -0,0 +1,73 @@
+# Moonlock
+
+A secure Wayland lockscreen with GTK4, PAM authentication and fingerprint support.
+Part of the Moonarch ecosystem.
+
+## Features
+
+- **ext-session-lock-v1** — Protocol-guaranteed screen locking (compositor keeps screen locked on crash)
+- **PAM authentication** — Uses system PAM stack (`/etc/pam.d/moonlock`)
+- **Fingerprint unlock** — fprintd D-Bus integration (optional)
+- **Multi-monitor** — Lockscreen on every monitor
+- **i18n** — German and English (auto-detected)
+- **Faillock warning** — UI counter + system pam_faillock
+- **Panic safety** — Panic hook logs but never unlocks
+- **Password wiping** — Zeroize on drop
+
+## Requirements
+
+- GTK 4
+- gtk4-session-lock (ext-session-lock-v1 support)
+- PAM (`/etc/pam.d/moonlock`)
+- Optional: fprintd for fingerprint support
+
+## Building
+
+```bash
+cargo build --release
+```
+
+## Installation
+
+```bash
+# Install binary
+sudo install -Dm755 target/release/moonlock /usr/bin/moonlock
+
+# Install PAM config
+sudo install -Dm644 config/moonlock-pam /etc/pam.d/moonlock
+
+# Optional: Install example config
+sudo install -Dm644 config/moonlock.toml.example /etc/moonlock/moonlock.toml.example
+```
+
+## Configuration
+
+Create `/etc/moonlock/moonlock.toml` or `~/.config/moonlock/moonlock.toml`:
+
+```toml
+background_path = "/usr/share/wallpapers/moon.jpg"
+fingerprint_enabled = true
+```
+
+## Usage
+
+Typically launched via keybind in your Wayland compositor:
+
+```
+# Niri keybind example
+binds {
+    Mod+L { spawn "moonlock"; }
+}
+```
+
+## Development
+
+```bash
+cargo test
+cargo build --release
+LD_PRELOAD=/usr/lib/libgtk4-layer-shell.so ./target/release/moonlock
+```
+
+## License
+
+MIT