Add lidarr-cleanup-singles package and integration

- Introduced a new package `lidarr-cleanup-singles` to identify and manage duplicate single tracks in Lidarr.
- Updated `flake.nix` to include the new package in outputs and modified app definitions to support it.
- Created a new script in `src-cleanup` for the main functionality, including audio fingerprint verification.
- Added necessary dependencies and configuration in `pyproject.toml` for the new package.
- Removed unused `flake-utils` and `systems` entries from `flake.lock` to streamline the configuration.

src-cleanup/pyproject.toml

@@ -0,0 +1,19 @@
+[build-system]
+requires = ["setuptools"]
+build-backend = "setuptools.build_meta"
+
+[tool.setuptools]
+py-modules = ["main"]
+
+[project]
+name = "lidarr-cleanup-singles"
+version = "1.0.0"
+description = "Identify and optionally delete duplicate single tracks in Lidarr"
+requires-python = ">=3.8"
+dependencies = [
+    "requests",
+]
+
+[project.scripts]
+lidarr-cleanup-singles = "main:main"
+