feat: add bread-sync module for snapshot and restore functionality

- Introduced `bread-sync` module with core functionalities for syncing system state via Git.
- Implemented `MachineProfile` struct for managing machine profiles, including methods for reading and writing profiles.
- Added package management support with snapshot capabilities for `pacman`, `pip`, `npm`, and `cargo`.
- Created comprehensive tests for sync operations, package parsing, and machine profile management.
- Enhanced `udev` adapter to include vendor and product IDs for scanned devices.
- Updated state engine to handle module clearing commands.
- Introduced Lua integration for accessing machine information and file system operations.
- Improved packaging documentation for Arch Linux and systemd service setup.

packaging/arch/README.md

@@ -1,9 +1,29 @@
 Arch packaging
 ==============
 
-This is a minimal PKGBUILD skeleton.
+`PKGBUILD` builds and installs both `breadd` and `bread` from source.
 
-Steps to use:
-- Update `pkgver`, `source`, `sha256sums`, and `url`.
-- Set the correct license and dependencies.
-- Ensure the release tarball includes `packaging/systemd/breadd.service`.
+## Local build
+
+```bash
+makepkg -si
+```
+
+## Before publishing to AUR
+
+1. Tag a release on GitHub.
+2. Update `pkgver` to match the tag.
+3. Update `source` to the release tarball URL.
+4. Run `updpkgsums` (or manually set `sha256sums`).
+5. Update `url` if the repository has moved.
+6. Set `depends` accurately — at minimum: `glibc`. Add `udev` and `libgit2` if not linking statically.
+
+## Runtime dependencies
+
+| Package | Required | Notes |
+|---------|----------|-------|
+| `glibc` | yes | always |
+| `udev` | yes | device events |
+| `dbus` | optional | UPower battery events |
+| `libnotify` | optional | `bread.notify()` (uses `notify-send`) |
+| `git` | optional | `bread sync` push/pull |