feat(flake): set up flake-parts

flake.lock

@@ -100,6 +100,26 @@
         "type": "github"
       }
     },
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1688466019,
+        "narHash": "sha256-VeM2akYrBYMsb4W/MmBo1zmaMfgbL4cH3Pu8PGyIwJ0=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "8e8d955c22df93dbe24f19ea04f47a74adbdc5ec",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -293,6 +313,7 @@
       "inputs": {
         "agenix": "agenix",
         "deploy-rs": "deploy-rs",
+        "flake-parts": "flake-parts",
         "flake-utils": "flake-utils",
         "home-manager": "home-manager_2",
         "nixos-hardware": "nixos-hardware",