Add flake.nix for Nix builds and dev shell

- Package builds with buildGoModule and CGO_ENABLED=0
- Dev shell provides go_latest, gopls, gotools

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,2 +1,3 @@
 /.apikey
 /pve-exporter
+/result

flake.lock

@@ -0,0 +1,43 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1773628058,
+        "narHash": "sha256-hpXH0z3K9xv0fHaje136KY872VT2T5uwxtezlAskQgY=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "f8573b9c935cfaa162dd62cc9e75ae2db86f85df",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs",
+        "systems": "systems"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,43 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    systems.url = "github:nix-systems/default";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    systems,
+  }: let
+    eachSystem = f:
+      nixpkgs.lib.genAttrs (import systems) (system:
+        f (import nixpkgs {inherit system;}));
+  in {
+    packages = eachSystem (pkgs: rec {
+      default = pve-exporter;
+      pve-exporter = pkgs.buildGoModule {
+        pname = "pve-exporter";
+        version = self.shortRev or self.dirtyShortRev or "dev";
+        src = ./.;
+        vendorHash = "sha256-VC80sdNcahVbxUffNNntlXWOg+ZDalck61d6tL9aWsM=";
+        env.CGO_ENABLED = 0;
+        ldflags = ["-s" "-w"];
+        doCheck = true;
+        meta = {
+          description = "Prometheus exporter for Proxmox VE";
+          mainProgram = "pve-exporter";
+        };
+      };
+    });
+
+    devShells = eachSystem (pkgs: {
+      default = pkgs.mkShell {
+        packages = with pkgs; [
+          go_latest
+          gopls
+          gotools
+        ];
+      };
+    });
+  };
+}