feat(renovate): enable lockFileMaintenance

This allows it to update the flake.lock and Cargo.lock files.

Also switch from a flake ref to a github ref as renovate cannot resolve
flake refs.

.renovaterc.json

@@ -24,10 +24,20 @@
     "fileMatch": [
       "(^|/)flake\\.nix$"
     ],
-    "commitMessageTopic": "flake inputs",
+    "commitMessageTopic": "nixpkgs",
     "commitMessageExtra": "to {{newValue}}",
     "enabled": true
   },
+  "lockFileMaintenance": {
+    "enabled": true,
+    "recreateWhen": "always",
+    "rebaseStalePrs": true,
+    "branchTopic": "lock-file-maintenance",
+    "commitMessageAction": "Lock file maintenance",
+    "schedule": [
+      "* 0-1 * * *"
+    ]
+  },
   "automergeSchedule": [
     "* 0-1 * * *"
   ]

flake.lock

@@ -37,17 +37,18 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1734424634,
+        "lastModified": 1735291276,
-        "narHash": "sha256-cHar1vqHOOyC7f1+tVycPoWTfKIaqkoe1Q6TnKzuti4=",
+        "narHash": "sha256-NYVcA06+blsLG6wpAbSPTCyLvxD/92Hy4vlY9WxFI1M=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "d3c42f187194c26d9f0309a8ecc469d6c878ce33",
+        "rev": "634fd46801442d760e09493a794c4f15db2d0cbb",
         "type": "github"
       },
       "original": {
-        "id": "nixpkgs",
+        "owner": "NixOS",
         "ref": "nixos-unstable",
-        "type": "indirect"
+        "repo": "nixpkgs",
+        "type": "github"
       }
     },
     "root": {

flake.nix

@@ -6,7 +6,7 @@
       url = "github:hercules-ci/flake-parts";
       inputs.nixpkgs-lib.follows = "nixpkgs";
     };
-    nixpkgs.url = "nixpkgs/nixos-unstable";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     systems.url = "github:nix-systems/default";
     treefmt-nix = {
       url = "github:numtide/treefmt-nix";