chore(nix): add flake support for build, run, and devShell

README.md

@@ -145,6 +145,48 @@ cargo build --release
 
 ---
 
+### ❄️ Nix (Flakes)
+
+A `flake.nix` is provided for [Nix](https://nixos.org/) users. Requires flakes
+enabled (`experimental-features = nix-command flakes` in `~/.config/nix/nix.conf`).
+
+**Run without installing:**
+
+```bash
+nix run github:timhartmann7/omnyssh
+nix run github:timhartmann7/omnyssh -- --theme dracula
+```
+
+**Build a local checkout:**
+
+```bash
+git clone https://github.com/timhartmann7/omnyssh.git
+cd omnyssh
+nix build              # binary at ./result/bin/omny
+./result/bin/omny --version
+```
+
+**Install into your user profile:**
+
+```bash
+nix profile install github:timhartmann7/omnyssh
+```
+
+**Develop with a pinned toolchain:**
+
+```bash
+nix develop            # drops you into a shell with rustc, cargo, clippy,
+                       # rustfmt, rust-analyzer, and all build inputs ready
+cargo build
+```
+
+The flake exposes `packages.default` (the `omny` binary plus man page),
+`apps.default` (for `nix run`), and `devShells.default`. It evaluates
+cleanly across `x86_64-linux`, `aarch64-linux`, `x86_64-darwin`, and
+`aarch64-darwin`.
+
+---
+
 ## Quick Start
 
 1. **Install OmnySSH** (see above)

flake.nix

@@ -0,0 +1,65 @@
+{
+  description = "OmnySSH — TUI SSH dashboard & server manager";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+
+        cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
+
+        omnyssh = pkgs.rustPlatform.buildRustPackage {
+          pname = cargoToml.package.name;
+          version = cargoToml.package.version;
+
+          src = self;
+
+          cargoLock = {
+            lockFile = ./Cargo.lock;
+          };
+
+          nativeBuildInputs = [ pkgs.pkg-config pkgs.installShellFiles ];
+
+          postInstall = ''
+            installManPage doc/omny.1
+          '';
+
+          meta = with pkgs.lib; {
+            description = cargoToml.package.description;
+            homepage = cargoToml.package.repository;
+            license = licenses.asl20;
+            mainProgram = "omny";
+          };
+        };
+      in
+      {
+        packages = {
+          default = omnyssh;
+          omnyssh = omnyssh;
+        };
+
+        apps.default = {
+          type = "app";
+          program = "${omnyssh}/bin/omny";
+          meta = omnyssh.meta;
+        };
+
+        devShells.default = pkgs.mkShell {
+          inputsFrom = [ omnyssh ];
+          packages = with pkgs; [
+            rustc
+            cargo
+            rustfmt
+            clippy
+            rust-analyzer
+          ];
+
+          RUST_SRC_PATH = "${pkgs.rustPlatform.rustLibSrc}";
+        };
+      });
+}